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International Court of Justice

The International Court of Justice (ICJ; Cour internationale de justice, CIJ), or colloquially the World Court, is the only international court that adjudicates general disputes between nations, and gives advisory opinions on international legal issues. It is one of the six organs of the United Nations (UN),   and is located in The Hague, Netherlands.

The ICJ is the successor of the Permanent Court of International Justice (PCIJ), which was established in 1920 by the League of Nations. After the Second World War, the League and the PCIJ were replaced by the United Nations and ICJ, respectively. The Statute of the ICJ, which sets forth its purpose and structure, draws heavily from that of its predecessor, whose decisions remain valid. All member states of the UN are party to the ICJ Statute and may initiate contentious legal cases; however, advisory proceedings may be submitted only by certain UN organs and agencies.

The ICJ consists of a panel of 15 judges elected by the UN General Assembly and Security Council for nine-year terms. No more than one judge of each nationality may be represented on court at the same time, and judges collectively must reflect the principal civilizations and legal systems of the world. Seated in the Peace Palace in The Hague, Netherlands, the ICJ is the only principal UN organ not located in New York City. Its official working languages are English and French.

Since the entry of its first case on 22 May 1947, the ICJ has entertained 191 cases through 13 November 2023. Pursuant to Article 59 of the Statute of the International Court of Justice, the court's rulings and opinions are binding on the parties with respect to the particular case ruled on by the court.

History
The first permanent institution established for the purpose of settling international disputes was the Permanent Court of Arbitration (PCA), which was created by the Hague Peace Conference of 1899. Initiated by the Russian Tsar Nicholas II, the conference involved all the world's major powers, as well as several smaller states, and resulted in the first multilateral treaties concerned with the conduct of warfare. Among these was the Convention for the Pacific Settlement of International Disputes, which set forth the institutional and procedural framework for arbitral proceedings, which would take place in The Hague, Netherlands. Although the proceedings would be supported by a permanent bureau—whose functions would be equivalent to that of a secretariat or court registry—the arbitrators would be appointed by the disputing states from a larger pool provided by each member of the convention. The PCA was established in 1900 and began proceedings in 1902.

A second Hague Peace Conference in 1907, which involved most of the world's sovereign states, revised the convention and enhanced the rules governing arbitral proceedings before the PCA. During this conference, the United States, Great Britain and Germany submitted a joint proposal for a permanent court whose judges would serve full-time. As the delegates could not agree how the judges would be selected, the matter was shelved pending an agreement to be adopted at a later convention.

The Hague Peace Conferences, and the ideas that emerged therefrom, influenced the creation of the Central American Court of Justice, which was established in 1908 as one of the earliest regional judicial bodies. Various plans and proposals were made between 1911 and 1919 for the establishment of an international judicial tribunal, which would not be realized in the formation of a new international system following the First World War.

The Permanent Court of International Justice
The unprecedented bloodshed of the First World War led to the creation of the League of Nations, established by the Paris Peace Conference of 1919 as the first worldwide intergovernmental organization aimed at maintaining peace and collective security. Article 14 League's Covenant called for the establishment of a Permanent Court of International Justice (PCIJ), which would be responsible for adjudicating any international dispute submitted to it by the contesting parties, as well as to provide an advisory opinion upon any dispute or question referred to it by the League of Nations.

In December 1920, following several drafts and debates, the Assembly of the league unanimously adopted the statute of the PCIJ, which was signed and ratified the following year by a majority of members. Among other things, the new Statute resolved the contentious issues of selecting judges by providing that the judges be elected by both the council and the Assembly of the league concurrently but independently. The makeup of the PCIJ would reflect the "main forms of civilization and the principal legal systems of the world". The PCIJ would be permanently placed at the Peace Palace in The Hague, alongside Permanent Court of Arbitration.

The PCIJ represented a major innovation in international jurisprudence in several ways:

 * Unlike previous international arbitral tribunals, it was a permanent body governed by its statutory provisions and rules of procedure
 * It had a permanent registry that served as a liaison with governments and international bodies
 * Its proceedings were largely public, including pleadings, oral arguments, and all documentary evidence
 * It was accessible to all states and could be declared by states to have compulsory jurisdiction over disputes
 * The PCIJ Statute was the first to list sources of law it would draw upon, which in turn became sources of international law
 * Judges were more representative of the world and its legal systems than any prior international judicial body

Unlike the ICJ, the PCIJ was not part of the league, nor were members of the league automatically a party to its Statute. The United States, which played a key role in both the second Hague Peace Conference and the Paris Peace Conference, was notably not a member of the league. However, several of its nationals served as judges of the court.

From its first session in 1922 until 1940, the PCIJ dealt with 29 interstate disputes and issued 27 advisory opinions. The court's widespread acceptance was reflected by the fact that several hundred international treaties and agreements conferred jurisdiction upon it over specified categories of disputes. In addition to helping resolve several serious international disputes, the PCIJ helped clarify several ambiguities in international law that contributed to its development.

The United States played a major role in setting up the PCIJ but never joined. Presidents Wilson, Harding, Coolidge, Hoover, and Roosevelt all supported membership, but it was impossible to get a two-thirds majority in the Senate for a treaty.

Establishment of the International Court of Justice
Following a peak of activity in 1933, the PCIJ began to decline in its activities due to the growing international tension and isolationism that characterized the era. The Second World War effectively put an end to the court, which held its last public session in December 1939 and issued its last orders in February 1940. In 1942 the United States and United Kingdom jointly declared support for establishing or re-establishing an international court after the war, and in 1943, the U.K. chaired a panel of jurists from around the world, the "Inter-Allied Committee", to discuss the matter. Its 1944 report recommended that:

 * The statute of any new international court should be based on that of the PCIJ;
 * The new court should retain an advisory jurisdiction;
 * Acceptance of the new court's jurisdiction should be voluntary;
 * The court should deal only with judicial and not political matters

Several months later at the Moscow conference in 1943, the major Allied Powers—China, the USSR, the U.K., and the U.S.—issued a joint declaration recognizing the necessity "of establishing at the earliest practicable date a general international organization, based on the principle of the sovereign equality of all peace-loving States, and open to membership by all such States, large and small, for the maintenance of international peace and security".

The following Allied conference at Dumbarton Oaks, in the United States, published a proposal in October 1944 that called for the establishment of an intergovernmental organization that would include an international court. A meeting was subsequently convened in Washington, D.C., in April 1945, involving 44 jurists from around the world to draft a statute for the proposed court. The draft statute was substantially similar to that of the PCIJ, and it was questioned whether a new court should even be created. During the San Francisco Conference, which took place from 25 April to 26 June 1945 and involved 50 countries, it was decided that an entirely new court should be established as a principal organ of the new United Nations. The statute of this court would form an integral part of the United Nations Charter, which, to maintain continuity, expressly held that the Statute of the International Court of Justice (ICJ) was based upon that of the PCIJ.

Consequently, the PCIJ convened for the last time in October 1945 and resolved to transfer its archives to its successor, which would take its place at the Peace Palace. The judges of the PCIJ all resigned on 31 January 1946, with the election of the first members of the ICJ taking place the following February at the First Session of the United Nations General Assembly and Security Council. In April 1946, the PCIJ was formally dissolved, and the ICJ, in its first meeting, was elected President José Gustavo Guerrero of El Salvador, who had served as the last president of the PCIJ. The court also appointed members of its Registry, mainly drawn from that of the PCIJ, and held an inaugural public sitting later that month.

The first case was submitted in May 1947 by the United Kingdom against Albania concerning incidents in the Corfu Channel.

Activities
Established in 1945 by the UN Charter, the court began work in 1946 as the successor to the Permanent Court of International Justice. The Statute of the International Court of Justice, similar to that of its predecessor, is the main constitutional document constituting and regulating the court.

The court's workload covers a wide range of judicial activity. After the court ruled that the United States's covert war against Nicaragua was in violation of international law (Nicaragua v. United States), the United States withdrew from compulsory jurisdiction in 1986 to accept the court's jurisdiction only on a discretionary basis. Chapter XIV of the United Nations Charter authorizes the UN Security Council to enforce Court rulings. However, such enforcement is subject to the veto power of the five permanent members of the council, which the United States used in the Nicaragua case.

Composition
The ICJ is composed of fifteen judges elected to nine-year terms by the UN General Assembly and the UN Security Council from a list of people nominated by the national groups in the Permanent Court of Arbitration. The election process is set out in Articles 4–19 of the ICJ Statute. Elections are staggered, with five judges elected every three years to ensure continuity within the court. Should a judge die in office, the practice has generally been to elect a judge in a special election to complete the term. Historically, deceased judges have been replaced by judges from the same region, though not —as often wrongly asserted— necessarily from the same nationality.

Article 3 states that no two judges may be nationals of the same country. According to Article 9, the membership of the court is supposed to represent the "main forms of civilization and of the principal legal systems of the world". This has been interpreted to include common law, civil law, socialist law, and Islamic law, while the precise meaning of "main forms of civilization" is contested.

There is an informal understanding that the seats will be distributed by geographic regions so that there are five seats for Western countries, three for African states (including one judge of Francophone civil law, one of Anglophone common law and one Arab), two for Eastern European states, three for Asian states and two for Latin American and Caribbean states. For most of the court's history, the five permanent members of the United Nations Security Council (France, USSR, China, the United Kingdom, and the United States) have always had a judge serving, thereby occupying three of the Western seats, one of the Asian seats and one of the Eastern European seats. Exceptions have been China not having a judge on the court from 1967 to 1985, during which time it did not put forward a candidate, and British judge Sir Christopher Greenwood being withdrawn as a candidate for election for a second nine-year term on the bench in 2017, leaving no judges from the United Kingdom on the court. Greenwood had been supported by the UN Security Council but failed to get a majority in the UN General Assembly. Indian judge Dalveer Bhandari took the seat instead.

Article 6 of the Statute provides that all judges should be "elected regardless of their nationality among persons of high moral character" who are either qualified for the highest judicial office in their home states or known as lawyers with sufficient competence in international law. Judicial independence is dealt with specifically in Articles 16–18.

To insure impartiality, Article 16 of the Charter requires independence from their national governements or other interested parties, stating, "No member of the Court may exercise any political or administrative function, or engage in any other occupation of a professional nature." In addition, Article 17 requires that judges do not show any prior biases on cases before them, specifically, "No member may participate in the decision of any case in which he has previously taken part as agent, counsel, or advocate for one of the parties, or as a member of a national or international court, or of a commission of enquiry, or in any other capacity."

Judges of the International Court of Justice are entitled to the style of His/Her Excellency. Judges are not able to hold any other post or act as counsel. In practice, members of the court have their own interpretation of these rules and many have chosen to remain involved in outside arbitration and hold professional posts as long as there is no conflict of interest. Former judge Bruno Simma and current judge Georg Nolte have acknowledged that moonlighting should be restricted.

A judge can be dismissed only by a unanimous vote of the other members of the court. Despite these provisions, the independence of ICJ judges has been questioned. For example, during the Nicaragua case, the United States issued a communiqué suggesting that it could not present sensitive material to the court because of the presence of judges from the Soviet bloc.

Judges may deliver joint judgments or give their own separate opinions. Decisions and advisory opinions are by majority, and, in the event of an equal division, the president's vote becomes decisive, which occurred in the Legality of the Use by a State of Nuclear Weapons in Armed Conflict (Opinion requested by WHO), [1996] ICJ Reports 66. Judges may also deliver separate dissenting opinions.

In its 77 years of history, only five women have been elected to the Court, with former UN Special Rapporteur Philip Alston calling for states to take seriously questions of representation in the bench.

In 2023, judges elected to take office from 2024 did not include a Russian member, so for the first time, from 2024 there will be no member from the Commonwealth of Independent States. This is also the first time that Russia would not have a judge on the ICJ, even going back to its predecessor, the Soviet Union.

Ad hoc judges
Article 31 of the statute sets out a procedure whereby ad hoc judges sit on contentious cases before the court. The system allows any party to a contentious case (if it otherwise does not have one of that party's nationals sitting on the court) to select one additional person to sit as a judge on that case only. It is thus possible that as many as seventeen judges may sit on one case.

The system may seem strange when compared with domestic court processes, but its purpose is to encourage states to submit cases. For example, if a state knows that it will have a judicial officer who can participate in deliberation and offer other judges local knowledge and an understanding of the state's perspective, it may be more willing to submit to the jurisdiction of the court. Although this system does not sit well with the judicial nature of the body, it is usually of little practical consequence. Ad hoc judges usually (but not always) vote in favour of the state that appointed them and thus cancel each other out.

Chambers
Generally, the court sits as full bench, but in the last fifteen years, it has on occasion sat as a chamber. Articles 26–29 of the statute allow the court to form smaller chambers, usually 3 or 5 judges, to hear cases. Two types of chambers are contemplated by Article 26: firstly, chambers for special categories of cases, and second, the formation of ad hoc chambers to hear particular disputes. In 1993, a special chamber was established, under Article 26(1) of the ICJ statute, to deal specifically with environmental matters (although it has never been used).

Ad hoc chambers are more frequently convened. For example, chambers were used to hear the Gulf of Maine Case (Canada/US). In that case, the parties made clear they would withdraw the case unless the court appointed judges to the chamber acceptable to the parties. Judgments of chambers may have either less authority than full Court judgments or diminish the proper interpretation of universal international law informed by a variety of cultural and legal perspectives. On the other hand, the use of chambers might encourage greater recourse to the court and thus enhance international dispute resolution.

Current composition
, the composition of the court is as follows:

Jurisdiction

As stated in Article 93 of the UN Charter, all UN members are automatically parties to the court's statute. Non-UN members may also become parties to the court's statute under the Article 93(2) procedure, which was used by Switzerland in 1948 and Nauru in 1988, prior to either joining the UN. Once a state is a party to the court's statute, it is entitled to participate in cases before the court. However, being a party to the statute does not automatically give the court jurisdiction over disputes involving those parties. The issue of jurisdiction is considered in the three types of ICJ cases: contentious issues, incidental jurisdiction, and advisory opinions.

Contentious issues
In contentious cases (adversarial proceedings seeking to settle a dispute), the ICJ produces a binding ruling between states that agree to submit to the ruling of the court. Only states may be parties in contentious cases; individuals, corporations, component parts of a federal state, NGOs, UN organs, and self-determination groups are excluded from direct participation, although the court may receive information from public international organizations. However, this does not preclude non-state interests from being the subject of proceedings; for example, a state may bring a case on behalf of one of its nationals or corporations, such as in matters concerning diplomatic protection.

Jurisdiction is often a crucial question for the court in contentious cases. The key principle is that the ICJ has jurisdiction only on the basis of consent. Under Article 36, there are four foundations for the court's jurisdiction: Additionally, the court may have jurisdiction on the basis of tacit consent (forum prorogatum). In the absence of clear jurisdiction under Article 36, jurisdiction is established if the respondent accepts ICJ jurisdiction explicitly or simply pleads on the merits. This arose in the 1949 Corfu Channel Case (U.K. v. Albania), in which the court held that a letter from Albania stating that it submitted to the jurisdiction of the ICJ was sufficient to grant the court jurisdiction.
 * 1) Compromis or "special agreement", in which parties provide explicit consent to the court's jurisdiction by referring cases to it. While not true compulsory jurisdiction, this is perhaps the most effective jurisdictional basis, because the parties concerned have a desire for the dispute to be resolved by the court, and are thus more likely to comply with the court's judgment.
 * 2) Compromissory clauses in a binding treaty. Most modern treaties contain such clauses to provide for dispute resolution by the ICJ. Cases founded on compromissory clauses have not been as effective as cases founded on special agreement, since a state may have no interest in having the matter examined by the court and may refuse to comply with a judgment. For example, during the Iran hostage crisis, Iran refused to participate in a case brought by the US based on a compromissory clause contained in the Vienna Convention on Diplomatic Relations and did not comply with the judgment. Since the 1970s, the use of such clauses has declined; many modern treaties set out their own dispute resolution regime, often based on forms of arbitration.
 * 3) Optional clause declarations accepting the court's jurisdiction. Also known as Article 36(2) jurisdiction, it is sometimes misleadingly labeled "compulsory", though such declarations are voluntary. Many such declarations contain reservations that exclude from jurisdiction certain types of disputes (ratione materia). The principle of reciprocity may further limit jurisdiction, as Article 36(2) holds that such declaration may be made "in relation to any other State accepting the same obligation...". As of January 2018, seventy-four states had a declaration in force, up from sixty-six in February 2011; of the permanent Security Council members, only the United Kingdom has a declaration. In the court's early years, most declarations were made by industrialized countries. Since the 1986 Nicaragua case, declarations made by developing countries have increased, reflecting a growing confidence in the court. However, even those industrialized countries that have invoked optional declarations have sometimes increased exclusions or rescinded them altogether. Notable examples include the United States in the Nicaragua case, and Australia, which modified its declaration in 2002 to exclude disputes on maritime boundaries, most likely to prevent an impending challenge from East Timor, which gained independence two months later.
 * 4) Article 36(5) provides for jurisdiction on the basis of declarations made under the Statute of the Permanent Court of International Justice. Article 37 similarly transfers jurisdiction under any compromissory clause in a treaty that gave jurisdiction to the PCIJ.

Incidental jurisdiction
Until rendering a final judgment, the court has competence to order interim measures for the protection of the rights of a party to a dispute. One or both parties to a dispute may apply the ICJ for issuing interim measures. In the Frontier Dispute Case, both parties to the dispute, Burkina Faso and Mali, submitted an application to the court to indicate interim measures. Incidental jurisdiction of the court derives from the Article 41 of its Statute. Similar to the final judgment, the order for interim measures of the court are binding on state parties to the dispute. The ICJ has competence to indicate interim measures only if the prima facie jurisdiction is satisfied.

Advisory opinions
An advisory opinion is a function of the court open only to specified United Nations bodies and agencies. The UN Charter grants the General Assembly or the Security Council the power to request the court to issue an advisory opinion on any legal question. Organs of the UN other than the General Assembly or the Security Council require the General Assembly's authorization to request an advisory opinion of the ICJ. These organs of the UN only request an advisory opinion regarding the matters that fall within the scope of their activities. On receiving a request, the court decides which states and organizations might provide useful information and gives them an opportunity to present written or oral statements. Advisory opinions were intended as a means by which UN agencies could seek the court's help in deciding complex legal issues that might fall under their respective mandates.

In principle, the court's advisory opinions are only consultative in character but they are influential and widely respected. Certain instruments or regulations can provide in advance that the advisory opinion shall be specifically binding on particular agencies or states, but inherently they are non-binding under the Statute of the court. This non-binding character does not mean that advisory opinions are without legal effect, because the legal reasoning embodied in them reflects the court's authoritative views on important issues of international law. In arriving at them, the court follows essentially the same rules and procedures that govern its binding judgments delivered in contentious cases submitted to it by sovereign states.

An advisory opinion derives its status and authority from the fact that it is the official pronouncement of the principal judicial organ of the United Nations.

Advisory opinions have often been controversial because the questions asked are controversial or the case was pursued as an indirect way of bringing what is really a contentious case before the court. Examples of advisory opinions can be found in the section advisory opinions in the List of International Court of Justice cases article. One such well-known advisory opinion is the Nuclear Weapons Case.

Examples of contentious cases

 * 1980: A complaint by the United States that Iran was detaining American diplomats in Tehran in violation of international law.
 * 1982: A dispute between Tunisia and Libya over the delimitation of the continental shelf between them.
 * 1989: A complaint by Iran after the shooting down of Iran Air Flight 655 by a United States Navy guided missile cruiser.
 * 1984: A dispute over the course of the maritime boundary dividing the U.S. and Canada in the Gulf of Maine area.
 * 1999: A complaint by the Federal Republic of Yugoslavia against the member states of the North Atlantic Treaty Organization regarding their actions in the Kosovo War. This was denied on 15 December 2004 because of lack of jurisdiction, the FRY not being a party to the ICJ statute at the time it made the application.
 * 2011: A complaint by the Republic of North Macedonia (former Yugoslav Republic of Macedonia) that Greece's vetoing of its accession to NATO violates the Interim Accord of 13 September 1995 between the two countries. The complaint was decided in favour of North Macedonia on 5 December 2011.
 * 2005: A complaint by the Democratic Republic of the Congo that its sovereignty had been violated by Uganda and that the DRC had lost billions of dollars worth of resources was decided in favour of the DRC.
 * 2017: A complaint by the Republic of India regarding a death penalty verdict against an Indian citizen, Kulbhushan Jadhav, by a Pakistani military court (based on alleged espionage and subversive activities).
 * 2022: A complaint by Ukraine against Russia for violating the 1948 Genocide Convention, to which both Ukraine and Russia are parties, by falsely claiming genocide as a pretext for invading Ukraine. The International Association of Genocide Scholars supported Ukraine, who asked for expedited provisional measures directing Russia to halt its offensive. Russian representatives refused to appear. On 16 March, the ICJ ordered Russia to "immediately suspend the military operations", on a 13–2 vote with the Russian and Chinese judges in opposition. The order is binding on Russia, but the ICJ cannot enforce it.

Relationship with UN Security Council
Article 94 establishes the duty of all UN members to comply with decisions of the court involving them. If parties do not comply, the issue may be taken before the Security Council for enforcement action. There are obvious problems with such a method of enforcement. If the judgment is against one of the five permanent members of the Security Council or its allies, any resolution on enforcement could then be vetoed by that member. That occurred, for example, after the Nicaragua case, when Nicaragua brought the issue of the United States' noncompliance with the court's decision before the Security Council. Furthermore, if the Security Council refuses to enforce a judgment against any other state, there is no method of forcing the state to comply. Furthermore, the most effective form to take action for the Security Council, coercive action under Chapter VII of the United Nations Charter, can be justified only if international peace and security are at stake. The Security Council has never done that so far.

The relationship between the ICJ and the Security Council, and the separation of their powers, was considered by the court in 1992 in the Pan Am case. The court had to consider an application from Libya for the order of provisional measures of protection to safeguard its rights, which, it alleged, were being infringed by the threat of economic sanctions by the United Kingdom and United States. The problem was that these sanctions had been authorized by the Security Council, which resulted in a potential conflict between the Chapter VII functions of the Security Council and the judicial function of the court. The court decided, by eleven votes to five, that it could not order the requested provisional measures because the rights claimed by Libya, even if legitimate under the 1971 Montreal Convention, could not be prima facie regarded as appropriate since the action was ordered by the Security Council. In accordance with Article 103 of the UN Charter, obligations under the Charter took precedence over other treaty obligations. Nevertheless, the court declared the application admissible in 1998. A decision on the merits has not been given since the parties (United Kingdom, United States, and Libya) settled the case out of court in 2003.

There was a marked reluctance on the part of a majority of the court to become involved in a dispute in such a way as to bring it potentially into conflict with the Council. The court stated in the Nicaragua case that there is no necessary inconsistency between action by the Security Council and adjudication by the ICJ. However, when there is room for conflict, the balance appears to be in favour of the Security Council.

Should either party fail "to perform the obligations incumbent upon it under a judgment rendered by the Court", the Security Council may be called upon to "make recommendations or decide upon measures" if the Security Council deems such actions necessary. In practice, the court's powers have been limited by the unwillingness of the losing party to abide by the court's ruling and by the Security Council's unwillingness to impose consequences. However, in theory, "so far as the parties to the case are concerned, a judgment of the Court is binding, final and without appeal", and "by signing the Charter, a State Member of the United Nations undertakes to comply with any decision of the International Court of Justice in a case to which it is a party."

For example, the United States had previously accepted the court's compulsory jurisdiction upon its creation in 1946 but in 1984, after Nicaragua v. United States, withdrew its acceptance following the court's judgment that called on the US to "cease and to refrain" from the "unlawful use of force" against the government of Nicaragua. The court ruled (with only the American judge dissenting) that the United States was "in breach of its obligation under the Treaty of Friendship with Nicaragua not to use force against Nicaragua" and ordered the United States to pay war reparations.

Law applied
When deciding cases, the court applies international law as summarized in Article 38 of the ICJ Statute, which provides that in arriving at its decisions the court shall apply international conventions, international custom and the "general principles of law recognized by civilized nations." It may also refer to academic writing ("the teachings of the most highly qualified publicists of the various nations") and previous judicial decisions to help interpret the law although the court is not formally bound by its previous decisions under the doctrine of stare decisis. Article 59 makes clear that the common law notion of precedent or stare decisis does not apply to the decisions of the ICJ. The court's decision binds only the parties to that particular controversy. Under 38(1)(d), however, the court may consider its own previous decisions and frequently cites them.

If the parties agree, they may also grant the court the liberty to decide ex aequo et bono ("out of equality, and for the good"), granting the ICJ the freedom to make an equitable decision based on what is fair under the circumstances. That provision has not been used in the court's history. So far, the International Court of Justice has dealt with about 180 cases.

Procedure
The ICJ is vested with the power to make its own rules. Court procedure is set out in the Rules of Court of the International Court of Justice 1978 (as amended on 29 September 2005).

Cases before the ICJ will follow a standard pattern. The case is lodged by the applicant, which files a written memorial setting out the basis of the court's jurisdiction and the merits of its claim. The respondent may accept the court's jurisdiction and file its own memorial on the merits of the case.

Preliminary objections
A respondent that does not wish to submit to the jurisdiction of the court may raise preliminary objections. Any such objections must be ruled upon before the court can address the merits of the applicant's claim. Often, a separate public hearing is held on the preliminary objections and the court will render a judgment. Respondents normally file preliminary objections to the jurisdiction of the court and/or the admissibility of the case. Inadmissibility refers to a range of arguments about factors the court should take into account in deciding jurisdiction, such as the fact that the issue is not justiciable or that it is not a "legal dispute".

In addition, objections may be made because all necessary parties are not before the court. If the case necessarily requires the court to rule on the rights and obligations of a state that has not consented to the court's jurisdiction, the court does not proceed to issue a judgment on the merits.

If the court decides it has jurisdiction and the case is admissible, the respondent then is required to file a Memorial addressing the merits of the applicant's claim. Once all written arguments are filed, the court holds a public hearing on the merits.

Once a case has been filed, any party (usually the applicant) may seek an order from the court to protect the status quo pending the hearing of the case. Such orders are known as Provisional (or Interim) Measures and are analogous to interlocutory injunctions in United States law. Article 41 of the statute allows the court to make such orders. The court must be satisfied to have prima facie jurisdiction to hear the merits of the case before it grants provisional measures.

Applications to intervene
In cases in which a third state's interests are affected, that state may be permitted to intervene in the case and participate as a full party. Under Article 62, a state "with an interest of a legal nature" may apply; however, it is within the court's discretion whether or not to allow the intervention. Intervention applications are rare, and the first successful application occurred only in 1991.

Judgment and remedies
Once deliberation has taken place, the court issues a majority opinion. Individual judges may issue concurring opinions (if they agree with the outcome reached in the judgment of the court but differ in their reasoning) or dissenting opinions (if they disagree with the majority). No appeal is possible, but any party may ask for the court to clarify if there is a dispute as to the meaning or scope of the court's judgment.

Criticisms
The International Court has been criticized with respect to its rulings, its procedures, and its authority. As with criticisms of the United Nations, many critics and opponents of the court refer to the general authority assigned to the body by member states through its Charter, rather than to specific problems with the composition of judges or their rulings. Major criticisms include the following:
 * "Compulsory" jurisdiction is limited to cases where both parties have agreed to submit to its decision, and so instances of aggression tend to be automatically escalated to and adjudicated by the Security Council. ICJ rulings are legally binding on states but not enforceable without their approval or compliance.
 * The International Court of Justice cannot hear the cases of organizations, private enterprises, and individuals. Furthermore, UN agencies are unable to raise a case except in the circumstance of a non-binding advisory opinion. The national states are the only ones who are able to bring cases for and act as defendants for these individuals. As a result, victims of war crimes, crimes against humanity and minority groups may not have the support of their national state.
 * Other existing international thematic courts, such as the ICC, are not under the umbrella of the International Court. Unlike ICJ, international thematic courts like ICC work independently from United Nations. Such dualistic structure between various international courts sometimes makes it hard for the courts to engage in effective and collective jurisdiction.
 * The International Court does not enjoy a full separation of powers, with permanent members of the Security Council being able to veto enforcement of cases, even those to which they consented to be bound. Because the jurisdiction does not have binding force itself, in many cases, the instances of aggression are adjudicated by Security Council by adopting a resolution, etc. There is, therefore, a likelihood for the permanent member states of Security Council to avoid the legal responsibility brought up by International Court of Justice, as shown in the example of Nicaragua v. United States.
 * The court has been accused of judicial parsimony, with its rulings tending to dismiss submissions of parties on jurisdictional grounds and not resolving the underlying dispute between them.
 * The court has been accused of exhibiting a political bias, with past research finding 'strong evidence' that judges at the ICJ 'favour the state that appoints them', 'favour states whose wealth level is close to that of the judges' own state', and 'favour states whose political system is similar to that of the judges' own state.'

Lectures

 * The ICJ in the Service of Peace and Justice, Conference organized on the Occasion of the Centenary of the Peace Palace
 * Lecture by Awn Shawkat Al-Khasawneh entitled "Reflections on the Jurisdiction of the International Court of Justice" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Mohamed Bennouna entitled "La Cour internationale de Justice, juge des souverainetés?" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Philippe Couvreur entitled "La Cour internationale de Justice" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Vera Gowlland-Debbas entitled "The International Court of Justice as the Principal Judicial Organ of the United Nations" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Mariko Kawano entitled "Some Salient Features of the Contemporary International Disputes in the Precedents of the International Court of Justice" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Mariko Kawano entitled "International Court of Justice and Disputes Involving the Interests of Third Parties to the Proceedings or the Common Interests of the International Community as a Whole or of the Community Established by a Convention" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Edward McWhinney entitled "Judicial Activism and the International Court of Justice" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Alain Pellet entitled "Conseil devant la Cour internationale de Justice" in the Lecture Series of the United Nations Audiovisual Library of International Law
 * Lecture by Jiuyong Shi entitled "The Present and Future Role of the International Court of Justice in the Peaceful Settlement of International Disputes" in the Lecture Series of the United Nations Audiovisual Library of International Law

title: International Court of Justice


text:
ISBN

The International Standard Book Number (ISBN) is a numeric commercial book identifier that is intended to be unique. Publishers purchase or receive ISBNs from an affiliate of the International ISBN Agency.

A different ISBN is assigned to each separate edition and variation of a publication, but not to a simple reprinting of an existing item. For example, an e-book, a paperback and a hardcover edition of the same book must each have a different ISBN, but an unchanged reprint of the hardcover edition keeps the same ISBN. The ISBN is ten digits long if assigned before 2007, and thirteen digits long if assigned on or after 1 January 2007. The method of assigning an ISBN is nation-specific and varies between countries, often depending on how large the publishing industry is within a country.

The first version of the ISBN identification format was devised in 1967, based upon the 9-digit Standard Book Numbering (SBN) created in 1966. The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108 (any 9-digit SBN can be converted to a 10-digit ISBN by prefixing it with a zero).

Privately published books sometimes appear without an ISBN. The International ISBN Agency sometimes assigns ISBNs to such books on its own initiative.

A separate identifier code of a similar kind, the International Standard Serial Number (ISSN), identifies periodical publications such as magazines and newspapers. The International Standard Music Number (ISMN) covers musical scores.

History
The Standard Book Number (SBN) is a commercial system using nine-digit code numbers to identify books. In 1965, British bookseller and stationers WHSmith announced plans to implement a standard numbering system for its books. They hired consultants to work on their behalf, and the system was devised by Gordon Foster, emeritus professor of statistics at Trinity College Dublin. The International Organization for Standardization (ISO) Technical Committee on Documentation sought to adapt the British SBN for international use. The ISBN identification format was conceived in 1967 in the United Kingdom by David Whitaker (regarded as the "Father of the ISBN") and in 1968 in the United States by Emery Koltay (who later became director of the U.S. ISBN agency R. R. Bowker).

The 10-digit ISBN format was developed by the ISO and was published in 1970 as international standard ISO 2108. The United Kingdom continued to use the nine-digit SBN code until 1974. ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide and the ISBN Standard is developed under the control of ISO Technical Committee 46/Subcommittee 9 TC 46/SC 9. The ISO on-line facility only refers back to 1978. An SBN may be converted to an ISBN by prefixing the digit "0". For example, the second edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has "SBN 340 01381 8", where "340" indicates the publisher, "01381" is the serial number assigned by the publisher, and "8" is the check digit. By prefixing a zero, this can be converted to ISBN 0-340-01381-8; the check digit does not need to be re-calculated. Some publishers, such as Ballantine Books, would sometimes use 12-digit SBNs where the last three digits indicated the price of the book; for example, Woodstock Handmade Houses had a 12-digit Standard Book Number of 345-24223-8-595 (valid SBN: 345-24223-8, ISBN: 0-345-24223-8), and it cost US$5.95.

Since 1 January 2007, ISBNs have contained thirteen digits, a format that is compatible with "Bookland" European Article Numbers, which have 13 digits.

The United States, with 3.9 million registered ISBNs in 2020, was by far the biggest user of the ISBN identifier in 2020, followed by the Republic of Korea (329,582), Germany (284,000), China (263,066), the UK (188,553) and Indonesia (144,793). Lifetime ISBNs registered in the United States are over 39 million as of 2020.

Overview
A separate ISBN is assigned to each edition and variation (except reprintings) of a publication. For example, an ebook, audiobook, paperback, and hardcover edition of the same book must each have a different ISBN assigned to it. The ISBN is thirteen digits long if assigned on or after 1 January 2007, and ten digits long if assigned before 2007. An International Standard Book Number consists of four parts (if it is a 10-digit ISBN) or five parts (for a 13-digit ISBN).

Section 5 of the International ISBN Agency's official user manual describes the structure of the 13-digit ISBN, as follows:

 * 1) for a 13-digit ISBN, a prefix element – a GS1 prefix: so far 978 or 979 have been made available by GS1,
 * 2) the registration group element (language-sharing country group, individual country or territory),
 * 3) the registrant element,
 * 4) the publication element, and
 * 5) a checksum character or check digit.

A 13-digit ISBN can be separated into its parts (prefix element, registration group, registrant, publication and check digit), and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts (registration group, registrant, publication and check digit) of a 10-digit ISBN is also done with either hyphens or spaces. Figuring out how to correctly separate a given ISBN is complicated, because most of the parts do not use a fixed number of digits.

Issuing process
ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for that country or territory regardless of the publication language. The ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned, and so the ranges will vary depending on the number of books and the number, type, and size of publishers that are active. Some ISBN registration agencies are based in national libraries or within ministries of culture and thus may receive direct funding from the government to support their services. In other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded.

A full directory of ISBN agencies is available on the International ISBN Agency website. A list for a few countries is given below:
 * Australia – Thorpe-Bowker
 * Brazil – The National Library of Brazil; (Up to 28 February 2020)
 * Brazil – Câmara Brasileira do Livro (From 1 March 2020)
 * Canada – English Library and Archives Canada, a government agency; French Bibliothèque et Archives nationales du Québec;
 * Colombia – Cámara Colombiana del Libro, an NGO
 * Hong Kong – Books Registration Office (BRO), under the Hong Kong Public Libraries
 * Iceland – Landsbókasafn (National and University Library of Iceland)
 * India – The Raja Rammohun Roy National Agency for ISBN (Book Promotion and Copyright Division), under Department of Higher Education, a constituent of the Ministry of Human Resource Development
 * Israel – The Israel Center for Libraries
 * Italy – EDISER srl, owned by Associazione Italiana Editori (Italian Publishers Association)
 * Kenya – National Library of Kenya
 * Latvia - Latvian ISBN Agency
 * Lebanon – Lebanese ISBN Agency
 * Maldives – The National Bureau of Classification (NBC)
 * Malta – The National Book Council (Il-Kunsill Nazzjonali tal-Ktieb)
 * Morocco – The National Library of Morocco
 * New Zealand – The National Library of New Zealand
 * Nigeria – National Library of Nigeria
 * Pakistan – National Library of Pakistan
 * Philippines – National Library of the Philippines
 * South Africa – National Library of South Africa
 * Spain – Spanish ISBN Agency – Agencia del ISBN
 * Turkey – General Directorate of Libraries and Publications, a branch of the Ministry of Culture
 * United Kingdom and Republic of Ireland – Nielsen Book Services Ltd, part of Nielsen Holdings N.V.
 * United States – R. R. Bowker

Registration group element
The ISBN registration group element is a 1-to-5-digit number that is valid within a single prefix element (i.e. one of 978 or 979), and can be separated between hyphens, such as "978-1-...". Registration groups have primarily been allocated within the 978 prefix element. The single-digit registration groups within the 978-prefix element are: 0 or 1 for English-speaking countries; 2 for French-speaking countries; 3 for German-speaking countries; 4 for Japan; 5 for Russian-speaking countries; and 7 for People's Republic of China. Example 5-digit registration groups are 99936 and 99980, for Bhutan. The allocated registration groups are: 0–5, 600–631, 65, 7, 80–94, 950–989, 9910–9989, and 99901–99993. Books published in rare languages typically have longer group elements.

Within the 979 prefix element, the registration group 0 is reserved for compatibility with International Standard Music Numbers (ISMNs), but such material is not actually assigned an ISBN. The registration groups within prefix element 979 that have been assigned are 8 for the United States of America, 10 for France, 11 for the Republic of Korea, and 12 for Italy.

The original 9-digit standard book number (SBN) had no registration group identifier, but prefixing a zero to a 9-digit SBN creates a valid 10-digit ISBN.

Registrant element
The national ISBN agency assigns the registrant element (cf. Category:ISBN agencies) and an accompanying series of ISBNs within that registrant element to the publisher; the publisher then allocates one of the ISBNs to each of its books. In most countries, a book publisher is not legally required to assign an ISBN, although most large bookstores only handle publications that have ISBNs assigned to them.

The International ISBN Agency maintains the details of over one million ISBN prefixes and publishers in the Global Register of Publishers. This database is freely searchable over the internet.

Publishers receive blocks of ISBNs, with larger blocks allotted to publishers expecting to need them; a small publisher may receive ISBNs of one or more digits for the registration group identifier, several digits for the registrant, and a single digit for the publication element. Once that block of ISBNs is used, the publisher may receive another block of ISBNs, with a different registrant element. Consequently, a publisher may have different allotted registrant elements. There also may be more than one registration group identifier used in a country. This might occur once all the registrant elements from a particular registration group have been allocated to publishers.

By using variable block lengths, registration agencies are able to customise the allocations of ISBNs that they make to publishers. For example, a large publisher may be given a block of ISBNs where fewer digits are allocated for the registrant element and many digits are allocated for the publication element; likewise, countries publishing many titles have few allocated digits for the registration group identifier and many for the registrant and publication elements. Here are some sample ISBN-10 codes, illustrating block length variations.

English language pattern
English-language registration group elements are 0 and 1 (2 of more than 220 registration group elements). These two registration group elements are divided into registrant elements in a systematic pattern, which allows their length to be determined, as follows:

Check digits
A check digit is a form of redundancy check used for error detection, the decimal equivalent of a binary check bit. It consists of a single digit computed from the other digits in the number. The method for the 10-digit ISBN is an extension of that for SBNs, so the two systems are compatible; an SBN prefixed with a zero (the 10-digit ISBN) will give the same check digit as the SBN without the zero. The check digit is base eleven, and can be an integer between 0 and 9, or an 'X'. The system for 13-digit ISBNs is not compatible with SBNs and will, in general, give a different check digit from the corresponding 10-digit ISBN, so does not provide the same protection against transposition. This is because the 13-digit code was required to be compatible with the EAN format, and hence could not contain the letter 'X'.

ISBN-10 check digits
According to the 2001 edition of the International ISBN Agency's official user manual, the ISBN-10 check digit (which is the last digit of the 10-digit ISBN) must range from 0 to 10 (the symbol 'X' is used for 10), and must be such that the sum of the ten digits, each multiplied by its (integer) weight, descending from 10 to 1, is a multiple of 11. That is, if x$i$ is the ith digit, then x$10$ must be chosen such that:

For example, for an ISBN-10 of 0-306-40615-2:

Formally, using modular arithmetic, this is rendered

It is also true for ISBN-10 s that the sum of all ten digits, each multiplied by its weight in ascending order from 1 to 10, is a multiple of 11. For this example:

Formally, this is rendered

The two most common errors in handling an ISBN (e.g. when typing it or writing it down) are a single altered digit or the transposition of adjacent digits. It can be proven mathematically that all pairs of valid ISBN-10 s differ in at least two digits. It can also be proven that there are no pairs of valid ISBN-10 s with eight identical digits and two transposed digits (these proofs are true because the ISBN is less than eleven digits long and because 11 is a prime number). The ISBN check digit method therefore ensures that it will always be possible to detect these two most common types of error, i.e., if either of these types of error has occurred, the result will never be a valid ISBN—the sum of the digits multiplied by their weights will never be a multiple of 11. However, if the error were to occur in the publishing house and remain undetected, the book would be issued with an invalid ISBN.

In contrast, it is possible for other types of error, such as two altered non-transposed digits, or three altered digits, to result in a valid ISBN (although it is still unlikely).

ISBN-10 check digit calculation
Each of the first nine digits of the 10-digit ISBN—excluding the check digit itself—is multiplied by its (integer) weight, descending from 10 to 2, and the sum of these nine products found. The value of the check digit is simply the one number between 0 and 10 which, when added to this sum, means the total is a multiple of 11.

For example, the check digit for an ISBN-10 of 0-306-40615-? is calculated as follows:

Adding 2 to 130 gives a multiple of 11 (because 132 = 12×11)—this is the only number between 0 and 10 which does so. Therefore, the check digit has to be 2, and the complete sequence is ISBN 0-306-40615-2. If the value of $$x_{10}$$ required to satisfy this condition is 10, then an 'X' should be used.

Alternatively, modular arithmetic is convenient for calculating the check digit using modulus 11. The remainder of this sum when it is divided by 11 (i.e. its value modulo 11), is computed. This remainder plus the check digit must equal either 0 or 11. Therefore, the check digit is (11 minus the remainder of the sum of the products modulo 11) modulo 11. Taking the remainder modulo 11 a second time accounts for the possibility that the first remainder is 0. Without the second modulo operation, the calculation could result in a check digit value of 11 − 0 = 11, which is invalid. (Strictly speaking, the first "modulo 11" is not needed, but it may be considered to simplify the calculation.)

For example, the check digit for the ISBN of 0-306-40615-? is calculated as follows:

Thus the check digit is 2.

It is possible to avoid the multiplications in a software implementation by using two accumulators. Repeatedly adding  into   computes the necessary multiples: The modular reduction can be done once at the end, as shown above (in which case  could hold a value as large as 496, for the invalid ISBN 99999-999-9-X ), or   and   could be reduced by a conditional subtract after each addition.

ISBN-13 check digit calculation
Appendix 1 of the International ISBN Agency's official user manual describes how the 13-digit ISBN check digit is calculated. The ISBN-13 check digit, which is the last digit of the ISBN, must range from 0 to 9 and must be such that the sum of all the thirteen digits, each multiplied by its (integer) weight, alternating between 1 and 3, is a multiple of 10. As ISBN-13 is a subset of EAN-13, the algorithm for calculating the check digit is exactly the same for both.

Formally, using modular arithmetic, this is rendered:

The calculation of an ISBN-13 check digit begins with the first twelve digits of the 13-digit ISBN (thus excluding the check digit itself). Each digit, from left to right, is alternately multiplied by 1 or 3, then those products are summed modulo 10 to give a value ranging from 0 to 9. Subtracted from 10, that leaves a result from 1 to 10. A zero replaces a ten, so, in all cases, a single check digit results.

For example, the ISBN-13 check digit of 978-0-306-40615-? is calculated as follows:

s = 9×1 + 7×3 + 8×1 + 0×3 + 3×1 + 0×3 + 6×1 + 4×3 + 0×1 + 6×3 + 1×1 + 5×3 =  9 +  21 +   8 +   0 +   3 +   0 +   6 +  12 +   0 +  18 +   1 +  15   = 93 93 / 10 = 9 remainder 3 10 – 3 = 7

Thus, the check digit is 7, and the complete sequence is ISBN 978-0-306-40615-7.

In general, the ISBN check digit is calculated as follows.

Let

Then

This check system—similar to the UPC check digit formula—does not catch all errors of adjacent digit transposition. Specifically, if the difference between two adjacent digits is 5, the check digit will not catch their transposition. For instance, the above example allows this situation with the 6 followed by a 1. The correct order contributes 3 × 6 + 1 × 1 = 19 to the sum; while, if the digits are transposed (1 followed by a 6), the contribution of those two digits will be 3 × 1 + 1 × 6 = 9. However, 19 and 9 are congruent modulo 10, and so produce the same, final result: both ISBNs will have a check digit of 7. The ISBN-10 formula uses the prime modulus 11 which avoids this blind spot, but requires more than the digits 0–9 to express the check digit.

Additionally, if the sum of the 2nd, 4th, 6th, 8th, 10th, and 12th digits is tripled then added to the remaining digits (1st, 3rd, 5th, 7th, 9th, 11th, and 13th), the total will always be divisible by 10 (i.e., end in 0).

ISBN-10 to ISBN-13 conversion
A 10-digit ISBN is converted to a 13-digit ISBN by prepending "978" to the ISBN-10 and recalculating the final checksum digit using the ISBN-13 algorithm. The reverse process can also be performed, but not for numbers commencing with a prefix other than 978, which have no 10-digit equivalent.

Errors in usage
Publishers and libraries have varied policies about the use of the ISBN check digit. Publishers sometimes fail to check the correspondence of a book title and its ISBN before publishing it; that failure causes book identification problems for libraries, booksellers, and readers. For example, ISBN 0-590-76484-5 is shared by two books—Ninja gaiden: a novel based on the best-selling game by Tecmo (1990) and Wacky laws (1997), both published by Scholastic.

Most libraries and booksellers display the book record for an invalid ISBN issued by the publisher. The Library of Congress catalogue contains books published with invalid ISBNs, which it usually tags with the phrase "Cancelled ISBN". The International Union Library Catalog (a.k.a., WorldCat OCLC—Online Computer Library Center system) often indexes by invalid ISBNs, if the book is indexed in that way by a member library.

eISBN
Only the term "ISBN" should be used; the terms "eISBN" and "e-ISBN" have historically been sources of confusion and should be avoided. If a book exists in one or more digital (e-book) formats, each of those formats must have its own ISBN. In other words, each of the three separate EPUB, Amazon Kindle, and PDF formats of a particular book will have its own specific ISBN. They should not share the ISBN of the paper version, and there is no generic "eISBN" which encompasses all the e-book formats for a title.

EAN format used in barcodes, and upgrading
The barcodes on a book's back cover (or inside a mass-market paperback book's front cover) are EAN-13; they may have a separate barcode encoding five digits called an EAN-5 for the currency and the recommended retail price. For 10-digit ISBNs, the number "978", the Bookland "country code", is prefixed to the ISBN in the barcode data, and the check digit is recalculated according to the EAN-13 formula (modulo 10, 1× and 3× weighting on alternating digits).

Partly because of an expected shortage in certain ISBN categories, the International Organization for Standardization (ISO) decided to migrate to a 13-digit ISBN ( ISBN-13 ). The process began on 1 January 2005 and was planned to conclude on 1 January 2007. , all the 13-digit ISBNs began with 978. As the 978 ISBN supply is exhausted, the 979 prefix was introduced. Part of the 979 prefix is reserved for use with the Musicland code for musical scores with an ISMN. The 10-digit ISMN codes differed visually as they began with an "M" letter; the bar code represents the "M" as a zero, and for checksum purposes it counted as a 3. All ISMNs are now thirteen digits commencing 979-0; 979-1 to 979-9 will be used by ISBN.

Publisher identification code numbers are unlikely to be the same in the 978 and 979 ISBNs, likewise, there is no guarantee that language area code numbers will be the same. Moreover, the 10-digit ISBN check digit generally is not the same as the 13-digit ISBN check digit. Because the GTIN-13 is part of the Global Trade Item Number (GTIN) system (that includes the GTIN-14, the GTIN-12, and the GTIN-8), the 13-digit ISBN falls within the 14-digit data field range.

Barcode format compatibility is maintained, because (aside from the group breaks) the ISBN-13 barcode format is identical to the EAN barcode format of existing 10-digit ISBNs. So, migration to an EAN-based system allows booksellers the use of a single numbering system for both books and non-book products that is compatible with existing ISBN based data, with only minimal changes to information technology systems. Hence, many booksellers (e.g., Barnes & Noble) migrated to EAN barcodes as early as March 2005. Although many American and Canadian booksellers were able to read EAN-13 barcodes before 2005, most general retailers could not read them. The upgrading of the UPC barcode system to full EAN-13, in 2005, eased migration to the ISBN in North America.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: ISBN


text:
IP address

An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface identification, and location addressing.

Internet Protocol version 4 (IPv4) defines an IP address as a 32-bit number. However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new version of IP (IPv6), using 128 bits for the IP address, was standardized in 1998. IPv6 deployment has been ongoing since the mid-2000s.

IP addresses are written and displayed in human-readable notations, such as in IPv4, and  in IPv6. The size of the routing prefix of the address is designated in CIDR notation by suffixing the address with the number of significant bits, e.g.,, which is equivalent to the historically used subnet mask.

The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to local Internet registries, such as Internet service providers (ISPs), and other end users. IPv4 addresses were distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each, but have been exhausted at the IANA level since 2011. Only one of the RIRs still has a supply for local assignments in Africa. Some IPv4 addresses are reserved for private networks and are not globally unique.

Network administrators assign an IP address to each device connected to a network. Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on network practices and software features. Some jurisdictions consider IP addresses to be personal data.

Function
An IP address serves two principal functions: it identifies the host, or more specifically, its network interface, and it provides the location of the host in the network, and thus, the capability of establishing a path to that host. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there." The header of each IP packet contains the IP address of the sending host and that of the destination host.

IP versions
Two versions of the Internet Protocol are in common use on the Internet today. The original version of the Internet Protocol that was first deployed in 1983 in the ARPANET, the predecessor of the Internet, is Internet Protocol version 4 (IPv4).

By the early 1990s, the rapid exhaustion of IPv4 address space available for assignment to Internet service providers and end-user organizations prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand addressing capability on the Internet. The result was a redesign of the Internet Protocol which became eventually known as Internet Protocol Version 6 (IPv6) in 1995. IPv6 technology was in various testing stages until the mid-2000s when commercial production deployment commenced.

Today, these two versions of the Internet Protocol are in simultaneous use. Among other technical changes, each version defines the format of addresses differently. Because of the historical prevalence of IPv4, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of version 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5.

Other versions v1 to v9 were defined, but only v4 and v6 ever gained widespread use. v1 and v2 were names for TCP protocols in 1974 and 1977, as there was no separate IP specification at the time. v3 was defined in 1978, and v3.1 is the first version where TCP is separated from IP. v6 is a synthesis of several suggested versions, v6 Simple Internet Protocol, v7 TP/IX: The Next Internet, v8 PIP — The P Internet Protocol, and v9 TUBA — Tcp & Udp with Big Addresses.

Subnetworks
IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP address is recognized as consisting of two parts: the network prefix in the high-order bits and the remaining bits called the rest field, host identifier, or interface identifier (IPv6), used for host numbering within a network. The subnet mask or CIDR notation determines how the IP address is divided into network and host parts.

The term subnet mask is only used within IPv4. Both IP versions however use the CIDR concept and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix. For example, an IPv4 address and its subnet mask may be and, respectively. The CIDR notation for the same IP address and subnet is, because the first 24 bits of the IP address indicate the network and subnet.

IPv4 addresses
An IPv4 address has a size of 32 bits, which limits the address space to 4 294  967  296 (232) addresses. Of this number, some addresses are reserved for special purposes such as private networks (≈18 million addresses) and multicast addressing (≈270 million addresses).

IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g.,. Each part represents a group of 8 bits (an octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

Subnetting history
In the early stages of development of the Internet Protocol, the network number was always the highest order octet (most significant eight bits). Because this method allowed for only 256 networks, it soon proved inadequate as additional networks developed that were independent of the existing networks already designated by a network number. In 1981, the addressing specification was revised with the introduction of classful network architecture.

Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes (B and C). The following table gives an overview of this now-obsolete system.

Classful network design served its purpose in the startup stage of the Internet, but it lacked scalability in the face of the rapid expansion of networking in the 1990s. The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrary-length prefixes. Today, remnants of classful network concepts function only in a limited scope as the default configuration parameters of some network software and hardware components (e.g. netmask), and in the technical jargon used in network administrators' discussions.

Private addresses
Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be globally unique. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.

Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses. Today, such private networks are widely used and typically connect to the Internet with network address translation (NAT), when needed.

Three non-overlapping ranges of IPv4 addresses for private networks are reserved. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry. Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of through.

IPv6 addresses

In IPv6, the address size was increased from 32 bits in IPv4 to 128 bits, thus providing up to 2128 (approximately $3.403$) addresses. This is deemed sufficient for the foreseeable future.

The intent of the new design was not to provide just a sufficient quantity of addresses, but also redesign routing in the Internet by allowing more efficient aggregation of subnetwork routing prefixes. This resulted in slower growth of routing tables in routers. The smallest possible individual allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization ratios will be small on any IPv6 network segment. The new design also provides the opportunity to separate the addressing infrastructure of a network segment, i.e. the local administration of the segment's available space, from the addressing prefix used to route traffic to and from external networks. IPv6 has facilities that automatically change the routing prefix of entire networks, should the global connectivity or the routing policy change, without requiring internal redesign or manual renumbering.

The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With a large address space, there is no need to have complex address conservation methods as used in CIDR.

All modern desktop and enterprise server operating systems include native support for IPv6, but it is not yet widely deployed in other devices, such as residential networking routers, voice over IP (VoIP) and multimedia equipment, and some networking hardware.

Private addresses
Just as IPv4 reserves addresses for private networks, blocks of addresses are set aside in IPv6. In IPv6, these are referred to as unique local addresses (ULAs). The routing prefix is reserved for this block, which is divided into two  blocks with different implied policies. The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.

Early practices used a different block for this purpose, dubbed site-local addresses. However, the definition of what constituted a site remained unclear and the poorly defined addressing policy created ambiguities for routing. This address type was abandoned and must not be used in new systems.

Addresses starting with, called link-local addresses, are assigned to interfaces for communication on the attached link. The addresses are automatically generated by the operating system for each network interface. This provides instant and automatic communication between all IPv6 hosts on a link. This feature is used in the lower layers of IPv6 network administration, such as for the Neighbor Discovery Protocol.

Private and link-local address prefixes may not be routed on the public Internet.

IP address assignment
IP addresses are assigned to a host either dynamically as they join the network, or persistently by configuration of the host hardware or software. Persistent configuration is also known as using a static IP address. In contrast, when a computer's IP address is assigned each time it restarts, this is known as using a dynamic IP address.

Dynamic IP addresses are assigned by network using Dynamic Host Configuration Protocol (DHCP). DHCP is the most frequently used technology for assigning addresses. It avoids the administrative burden of assigning specific static addresses to each device on a network. It also allows devices to share the limited address space on a network if only some of them are online at a particular time. Typically, dynamic IP configuration is enabled by default in modern desktop operating systems.

The address assigned with DHCP is associated with a lease and usually has an expiration period. If the lease is not renewed by the host before expiry, the address may be assigned to another device. Some DHCP implementations attempt to reassign the same IP address to a host, based on its MAC address, each time it joins the network. A network administrator may configure DHCP by allocating specific IP addresses based on MAC address.

DHCP is not the only technology used to assign IP addresses dynamically. Bootstrap Protocol is a similar protocol and predecessor to DHCP. Dialup and some broadband networks use dynamic address features of the Point-to-Point Protocol.

Computers and equipment used for the network infrastructure, such as routers and mail servers, are typically configured with static addressing.

In the absence or failure of static or dynamic address configurations, an operating system may assign a link-local address to a host using stateless address autoconfiguration.

Sticky dynamic IP address
Sticky is an informal term used to describe a dynamically assigned IP address that seldom changes. IPv4 addresses, for example, are usually assigned with DHCP, and a DHCP service can use rules that maximize the chance of assigning the same address each time a client asks for an assignment. In IPv6, a prefix delegation can be handled similarly, to make changes as rare as feasible. In a typical home or small-office setup, a single router is the only device visible to an Internet service provider (ISP), and the ISP may try to provide a configuration that is as stable as feasible, i.e. sticky. On the local network of the home or business, a local DHCP server may be designed to provide sticky IPv4 configurations, and the ISP may provide a sticky IPv6 prefix delegation, giving clients the option to use sticky IPv6 addresses. Sticky should not be confused with static; sticky configurations have no guarantee of stability, while static configurations are used indefinitely and only changed deliberately.

Address autoconfiguration
Address block is defined for the special use of link-local addressing for IPv4 networks. In IPv6, every interface, whether using static or dynamic addresses, also receives a link-local address automatically in the block. These addresses are only valid on the link, such as a local network segment or point-to-point connection, to which a host is connected. These addresses are not routable and, like private addresses, cannot be the source or destination of packets traversing the Internet.

When the link-local IPv4 address block was reserved, no standards existed for mechanisms of address autoconfiguration. Filling the void, Microsoft developed a protocol called Automatic Private IP Addressing (APIPA), whose first public implementation appeared in Windows 98. APIPA has been deployed on millions of machines and became a de facto standard in the industry. In May 2005, the IETF defined a formal standard for it.

Addressing conflicts
An IP address conflict occurs when two devices on the same local physical or wireless network claim to have the same IP address. A second assignment of an address generally stops the IP functionality of one or both of the devices. Many modern operating systems notify the administrator of IP address conflicts. When IP addresses are assigned by multiple people and systems with differing methods, any of them may be at fault. If one of the devices involved in the conflict is the default gateway access beyond the LAN for all devices on the LAN, all devices may be impaired.

Routing
IP addresses are classified into several classes of operational characteristics: unicast, multicast, anycast and broadcast addressing.

Unicast addressing
The most common concept of an IP address is in unicast addressing, available in both IPv4 and IPv6. It normally refers to a single sender or a single receiver, and can be used for both sending and receiving. Usually, a unicast address is associated with a single device or host, but a device or host may have more than one unicast address. Sending the same data to multiple unicast addresses requires the sender to send all the data many times over, once for each recipient.

Broadcast addressing
Broadcasting is an addressing technique available in IPv4 to address data to all possible destinations on a network in one transmission operation as an all-hosts broadcast. All receivers capture the network packet. The address is used for network broadcast. In addition, a more limited directed broadcast uses the all-ones host address with the network prefix. For example, the destination address used for directed broadcast to devices on the network is.

IPv6 does not implement broadcast addressing and replaces it with multicast to the specially defined all-nodes multicast address.

Multicast addressing
A multicast address is associated with a group of interested receivers. In IPv4, addresses through  (the former Class D addresses) are designated as multicast addresses. IPv6 uses the address block with the prefix for multicast. In either case, the sender sends a single datagram from its unicast address to the multicast group address and the intermediary routers take care of making copies and sending them to all interested receivers (those that have joined the corresponding multicast group).

Anycast addressing
Like broadcast and multicast, anycast is a one-to-many routing topology. However, the data stream is not transmitted to all receivers, just the one which the router decides is closest in the network. Anycast addressing is a built-in feature of IPv6. In IPv4, anycast addressing is implemented with Border Gateway Protocol using the shortest-path metric to choose destinations. Anycast methods are useful for global load balancing and are commonly used in distributed DNS systems.

Geolocation
A host may use geolocation to deduce the geographic position of its communicating peer. This is typically done by retrieving geolocation info about the IP address of the other node from a database.

Public address
A public IP address is a globally routable unicast IP address, meaning that the address is not an address reserved for use in private networks, such as those reserved by, or the various IPv6 address formats of local scope or site-local scope, for example for link-local addressing. Public IP addresses may be used for communication between hosts on the global Internet. In a home situation, a public IP address is the IP address assigned to the home's network by the ISP. In this case, it is also locally visible by logging into the router configuration.

Most public IP addresses change, and relatively often. Any type of IP address that changes is called a dynamic IP address. In home networks, the ISP usually assigns a dynamic IP. If an ISP gave a home network an unchanging address, it is more likely to be abused by customers who host websites from home, or by hackers who can try the same IP address over and over until they breach a network.

Address translation
Multiple client devices can appear to share an IP address, either because they are part of a shared web hosting service environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of the client, in which case the real originating IP address is masked from the server receiving a request. A common practice is to have a NAT mask many devices in a private network. Only the public interface(s) of the NAT needs to have an Internet-routable address.

The NAT device maps different IP addresses on the private network to different TCP or UDP port numbers on the public network. In residential networks, NAT functions are usually implemented in a residential gateway. In this scenario, the computers connected to the router have private IP addresses and the router has a public address on its external interface to communicate on the Internet. The internal computers appear to share one public IP address.

Law
In March 2024, the Supreme Court of Canada decided that IP addresses were protected private information under the Canadian Charter of Rights and Freedoms, with police searches requiring a warrant in order to obtain them. IP addresses are considered personal data by the European Commission and are protected by the General Data Protection Regulation.

Diagnostic tools
Computer operating systems provide various diagnostic tools to examine network interfaces and address configuration. Microsoft Windows provides the command-line interface tools ipconfig and netsh and users of Unix-like systems may use ifconfig, netstat, route, lanstat, fstat, and iproute2 utilities to accomplish the task.

title: IP address


text:
If and only if

In logic and related fields such as mathematics and philosophy, "if and only if" (often shortened as "iff") is paraphrased by the biconditional, a logical connective between statements. The biconditional is true in two cases, where either both statements are true or both are false. The connective is biconditional (a statement of material equivalence), and can be likened to the standard material conditional ("only if", equal to "if ... then") combined with its reverse ("if"); hence the name. The result is that the truth of either one of the connected statements requires the truth of the other (i.e. either both statements are true, or both are false), though it is controversial whether the connective thus defined is properly rendered by the English "if and only if"—with its pre-existing meaning. For example, P if and only if Q means that P is true whenever Q is true, and the only case in which P is true is if Q is also true, whereas in the case of P if Q, there could be other scenarios where P is true and Q is false.

In writing, phrases commonly used as alternatives to P "if and only if" Q include: Q is necessary and sufficient for P, for P it is necessary and sufficient that Q, P is equivalent (or materially equivalent) to Q (compare with material implication), P precisely if Q, P precisely (or exactly) when Q, P exactly in case Q, and P just in case Q. Some authors regard "iff" as unsuitable in formal writing; others consider it a "borderline case" and tolerate its use. In logical formulae, logical symbols, such as $$\leftrightarrow$$ and $$\Leftrightarrow$$, are used instead of these phrases; see below.

Definition
The truth table of P $$\leftrightarrow$$ Q is as follows:

It is equivalent to that produced by the XNOR gate, and opposite to that produced by the XOR gate.

Notation
The corresponding logical symbols are "$$\leftrightarrow$$", "$$\Leftrightarrow$$", and $$\equiv$$, and sometimes "iff". These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas (e.g., in metalogic). In Łukasiewicz's Polish notation, it is the prefix symbol $$E$$.

Another term for the logical connective, i.e., the symbol in logic formulas, is exclusive nor.

In TeX, "if and only if" is shown as a long double arrow: $$\iff$$ via command \iff or \Longleftrightarrow.

Proofs
In most logical systems, one proves a statement of the form "P iff Q" by proving either "if P, then Q" and "if Q, then P", or "if P, then Q" and "if not-P, then not-Q". Proving these pairs of statements sometimes leads to a more natural proof, since there are not obvious conditions in which one would infer a biconditional directly. An alternative is to prove the disjunction "(P and Q) or (not-P and not-Q)", which itself can be inferred directly from either of its disjuncts—that is, because "iff" is truth-functional, "P iff Q" follows if P and Q have been shown to be both true, or both false.

Origin of iff and pronunciation
Usage of the abbreviation "iff" first appeared in print in John L. Kelley's 1955 book General Topology. Its invention is often credited to Paul Halmos, who wrote "I invented 'iff,' for 'if and only if'—but I could never believe I was really its first inventor."

It is somewhat unclear how "iff" was meant to be pronounced. In current practice, the single 'word' "iff" is almost always read as the four words "if and only if". However, in the preface of General Topology, Kelley suggests that it should be read differently: "In some cases where mathematical content requires 'if and only if' and euphony demands something less I use Halmos' 'iff'". The authors of one discrete mathematics textbook suggest: "Should you need to pronounce iff, really hang on to the 'ff' so that people hear the difference from 'if'", implying that "iff" could be pronounced as.

Usage in definitions
Conventionally, definitions are "if and only if" statements; some texts — such as Kelley's General Topology — follow this convention, and use "if and only if" or iff in definitions of new terms. However, this usage of "if and only if" is relatively uncommon and overlooks the linguistic fact that the "if" of a definition is interpreted as meaning "if and only if". The majority of textbooks, research papers and articles (including English Wikipedia articles) follow the linguistic convention of interpreting "if" as "if and only if" whenever a mathematical definition is involved (as in "a topological space is compact if every open cover has a finite subcover"). Moreover, in the case of a recursive definition, the only if half of the definition is interpreted as a sentence in the metalanguage stating that the sentences in the definition of a predicate are the only sentences determining the extension of the predicate.

In terms of Euler diagrams
Euler diagrams show logical relationships among events, properties, and so forth. "P only if Q", "if P then Q", and "P→Q" all mean that P is a subset, either proper or improper, of Q. "P if Q", "if Q then P", and Q→P all mean that Q is a proper or improper subset of P. "P if and only if Q" and "Q if and only if P" both mean that the sets P and Q are identical to each other.

More general usage
Iff is used outside the field of logic as well. Wherever logic is applied, especially in mathematical discussions, it has the same meaning as above: it is an abbreviation for if and only if, indicating that one statement is both necessary and sufficient for the other. This is an example of mathematical jargon (although, as noted above, if is more often used than iff in statements of definition).

The elements of X are all and only the elements of Y means: "For any z in the domain of discourse, z is in X if and only if z is in Y."

When "if" means "if and only if"
In their Artificial Intelligence: A Modern Approach, Russell and Norvig note (page 282), in effect, that it is often more natural to express if and only if as if together with a "database (or logic programming) semantics". They give the example of the English sentence "Richard has two brothers, Geoffrey and John".

In a database or logic program, this could be represented simply by two sentences:

 * Brother(Richard, Geoffrey).
 * Brother(Richard, John).

The database semantics interprets the database (or program) as containing all and only the knowledge relevant for problem solving in a given domain. It interprets only if as expressing in the metalanguage that the sentences in the database represent the only knowledge that should be considered when drawing conclusions from the database.

In first-order logic (FOL) with the standard semantics, the same English sentence would need to be represented, using if and only if, with only if interpreted in the object language, in some such form as:

 * $$\forall $$ X(Brother(Richard, X) iff X = Geoffrey or X = John).
 * Geoffrey ≠ John.

Compared with the standard semantics for FOL, the database semantics has a more efficient implementation. Instead of reasoning with sentences of the form:

 * conclusion iff conditions

it uses sentences of the form:

 * conclusion if conditions

to reason forwards from conditions to conclusions or backwards from conclusions to conditions.

The database semantics is analogous to the legal principle expressio unius est exclusio alterius (the express mention of one thing excludes all others). Moreover, it underpins the application of logic programming to the representation of legal texts and legal reasoning.

title: If and only if


text:
IP

IP most often refers to :
 * Intellectual property, creations of the mind for which exclusive legal rights are recognized
 * Internet Protocol, a set of rules for sending data across a network

IP or Ip or ip may also refer to:

Businesses and organizations

 * IP College (Indraprastha College for Women), a constituent college of the University of Delhi, New Delhi, India
 * Imperial Police, a former Indian police agency
 * Inicjatywa Pracownicza (Workers' Initiative), a Polish trade union
 * International Paper, an American pulp and paper company
 * Iraqi Police
 * Atyrau Airways (IATA code: IP)
 * Italiana Petroli, an Italian petroleum brand owned by Anonima Petroli Italiana

Places

 * Ipswich, for Ipswich and surrounding areas, England
 * Ip, Sălaj, Romania
 * Ip (river), a river in Sălaj County, Romania
 * IP Casino Resort Spa, in Biloxi, Mississippi, US

Biology and medicine

 * Immunoprecipitation, a molecular biology technique
 * Incontinentia pigmenti, a genetic disorder
 * Infundibulopelvic ligament, part of the female pelvis
 * Interphalangeal joint (disambiguation)
 * Interventional pulmonology, a less invasive lung treatment than surgery
 * Intestinal permeability
 * Intraperitoneal injection (IP injection), the injection of a substance into the peritoneum
 * Prostacyclin receptor (symbol PTGIR, older synonym IP)

Computing

 * IP address, a numerical label assigned to each device connected to a computer network
 * IP (complexity), a class in computational complexity theory
 * IP core (intellectual property core), a reusable design unit owned by one party
 * Instruction pointer, a processor register
 * Intelligent Peripheral, a part of a public telecommunications Intelligent Network
 * Image processing
 * , a Linux command in the iproute2 collection

Other science and technology

 * IP code (Ingress Protection code), an equipment protection classification scheme
 * Identified patient, a psychology term
 * Identity preserved, an agricultural designation
 * Induced polarization, a geophysical imaging technique
 * Intercept point, a measure in amplifiers and mixers
 * Ion plating, a chemical process

Law and government

 * Inspector of Police, a rank in police forces of India.
 * Industrial property, similar to intellectual property but including trademarks and excluding artistic copyright
 * Insolvency practitioner, a legal specialist
 * Industrial policy, a country's effort to encourage the development of certain sectors of the economy
 * Integrated project (EU), a type of research project
 * Immunity passport
 * I/P, sometimes used as shorthand for the Israeli–Palestinian conflict

Other uses

 * Ip (cuneiform)
 * Ip (surname)
 * Inflectional phrase, a functional phrase that has inflectional properties
 * Innings pitched, a baseball statistic
 * Integrated Programme, an academic scheme in Singapore
 * Internationale Politik, a German political journal
 * Item and Process, a linguistic method to describe phenomena of allomorphy

title: IP