Why This Matters
International law without courts is aspiration. The ICJ and the ICC represent the two judicial pillars of the international legal order. The ICJ resolves disputes between states: it is the principal judicial organ of the UN, the successor to the PCIJ, and the court to which states bring their most consequential legal claims. The ICC holds individuals criminally responsible for the worst crimes known to international law: genocide, crimes against humanity, war crimes, and the crime of aggression. Together they represent the proposition that in international law, as in domestic law, both states and individuals are accountable to binding rules enforced by independent courts. The OU examiner tests both consistently, with ICJ jurisdiction and ICC complementarity generating the highest frequency of exam questions across the PYQ analysis papers.
Chapter Overview
This chapter answers four questions:
- What is the ICJ? Its composition, jurisdiction, and procedure.
- How does the ICJ decide cases? Contentious jurisdiction and advisory opinions.
- What is the ICC? Its establishment, jurisdiction, and the complementarity principle.
- How do the ICJ and ICC differ? Their functions, jurisdiction, and relationship.
The International Court of Justice
Composition and Establishment
The International Court of Justice is the principal judicial organ of the United Nations, established by the UN Charter and the ICJ Statute, which entered into force on 24 October 1945.
The ICJ is the successor to the Permanent Court of International Justice (PCIJ), which functioned from 1920 to 1945 under the League of Nations. The ICJ Statute is almost identical to the PCIJ Statute and is an integral part of the UN Charter under Article 92.
The Court consists of 15 judges elected by concurrent vote of the General Assembly and the Security Council for nine-year terms. Judges sit in their personal capacity: they do not represent their states and are expected to be independent. A state party to a case that has no judge of its nationality on the bench may appoint an ad hoc judge for that case.
The Court sits at the Peace Palace in The Hague, Netherlands.
📋 What it addresses: The composition, jurisdiction, and procedure of the ICJ as the principal judicial organ of the UN.
📌 Key Articles: Article 34: only states may be parties in contentious cases. Article 36: basis of jurisdiction. Article 38: sources of international law applicable. Article 59: binding effect of judgments only between parties and in the case decided. Article 65: advisory opinion jurisdiction.
🎯 Significance: Integral part of the UN Charter. The ICJ Statute Article 38(1) is the most authoritative statement of the sources of international law in existence.
Jurisdiction of the ICJ
The ICJ has two types of jurisdiction: contentious jurisdiction over disputes between states, and advisory jurisdiction to give opinions on legal questions.
Contentious Jurisdiction
Only states may be parties in contentious cases before the ICJ under Article 34. International organisations, individuals, and corporations cannot bring or face claims before the ICJ. The ICJ has no compulsory jurisdiction: it can hear a case only if the respondent state has consented to its jurisdiction.
Consent to ICJ jurisdiction is established in four ways.
Special agreement (compromis): Both states agree after the dispute arises to submit it to the ICJ. The most straightforward basis.
Treaty clause: Many treaties contain a clause submitting disputes about the treaty's interpretation or application to the ICJ. If both parties to the dispute have ratified that treaty, the clause constitutes consent.
Optional clause declaration (Article 36(2)): A state may make a unilateral declaration accepting the compulsory jurisdiction of the ICJ as binding in relation to any other state that has made a similar declaration. These declarations may contain reservations limiting their scope. The system of optional clause declarations creates a network of reciprocal jurisdictional commitments.
Forum prorogatum: A state that has not formally consented may implicitly accept jurisdiction by participating in proceedings without contesting jurisdiction. Rare but recognised.
The ICJ determines its own jurisdiction under the principle of kompetenz-kompetenz: if a state contests jurisdiction, the ICJ rules on that preliminary objection before proceeding to the merits.
S pecial agreement: both states consent after dispute arises
T reaty clause: dispute settlement provision in applicable treaty
O ptional clause: Article 36(2) unilateral declaration with reciprocity
F orum prorogatum: implicit acceptance through participation
Advisory Jurisdiction
The ICJ may give advisory opinions on any legal question at the request of the General Assembly, the Security Council, or other UN organs and specialised agencies authorised by the General Assembly.
Advisory opinions are not binding. They carry significant legal authority and are treated as highly persuasive statements of international law, but they create no legal obligation on the requesting organ or on states. States cannot request advisory opinions directly: only UN organs and authorised international organisations can.
Notable advisory opinions include: Reservations to the Genocide Convention (1951), Reparation for Injuries (1949), Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory (2004), and Kosovo Independence (2010).
Procedure and Judgments
ICJ proceedings have two phases: written pleadings (memorials, counter-memorials, replies) and oral hearings. The Court deliberates in private and delivers its judgment by majority vote. Each judge may append a separate opinion (concurring or dissenting).
Article 59: The decision of the Court has no binding force except between the parties and in respect of the particular case. The ICJ does not formally follow precedent (stare decisis does not apply in international law) but in practice the Court's decisions are highly consistent and its earlier judgments are treated as authoritative.
Article 94 of the UN Charter: Each member state undertakes to comply with ICJ judgments in cases to which it is a party. If a state fails to comply, the other party may have recourse to the Security Council, which may make recommendations or decide measures to give effect to the judgment. The veto means that enforcement against a P5 state or its ally is practically impossible.
The International Criminal Court
Establishment and Structure
The International Criminal Court was established by the Rome Statute, adopted on 17 July 1998 and entering into force on 1 July 2002.
The ICC is the first permanent international criminal court with jurisdiction over individuals for the most serious crimes of international concern. It is not a UN organ: it is an independent international organisation with its own legal personality, established by treaty. It has a relationship agreement with the UN but operates independently.
The ICC is seated in The Hague. It has 124 states parties as of 2024. Major non-parties include the USA (signed but withdrew signature), Russia (signed but withdrew signature), China, and India.
The Court comprises four organs: the Presidency, the Judicial Divisions (Pre-Trial, Trial, and Appeals), the Office of the Prosecutor, and the Registry.
📋 What it addresses: The establishment, jurisdiction, admissibility, applicable law, and procedure of the ICC for international crimes.
📌 Key Articles: Article 5: crimes within the jurisdiction. Article 12: preconditions to jurisdiction. Article 17: complementarity and admissibility. Article 25: individual criminal responsibility. Article 27: irrelevance of official capacity. Article 98: immunity and surrender.
🎯 Significance: First permanent international criminal court. 124 states parties. Complementarity principle makes it a court of last resort, activating only when national systems fail.
Jurisdiction of the ICC
The ICC has jurisdiction over four categories of crime under Article 5 of the Rome Statute.
Genocide: Acts committed with intent to destroy, in whole or in part, a national, ethnic, racial, or religious group. Includes killing, causing serious bodily or mental harm, deliberately inflicting conditions of life calculated to bring about physical destruction, imposing measures to prevent births, and forcibly transferring children.
Crimes against humanity: Widespread or systematic attacks directed against any civilian population, including murder, extermination, enslavement, deportation, torture, rape, persecution, enforced disappearance, apartheid, and other inhumane acts.
War crimes: Grave breaches of the Geneva Conventions and other serious violations of the laws and customs applicable in armed conflict, both international and non-international.
The crime of aggression: Added by the Kampala Amendment (2010), entering into force for states parties that ratified the amendment in 2018. Covers the planning, preparation, initiation, or execution by a person in a leadership position of an act of aggression by a state against another state.
Preconditions to Jurisdiction
The ICC may exercise jurisdiction only if one of the following conditions is satisfied.
The crime was committed on the territory of a state party, or the accused is a national of a state party. Alternatively, a state that is not a party may accept the Court's jurisdiction for a specific situation. Additionally, the Security Council may refer a situation to the Prosecutor under Chapter VII of the UN Charter, regardless of whether the state concerned is a party to the Rome Statute.
The Security Council referral mechanism is significant: it allows the ICC to reach crimes committed in non-party states. The Security Council referred the situations in Darfur (Sudan, 2005) and Libya (2011) to the ICC under this mechanism.
The Complementarity Principle
The ICC is a court of last resort, not a substitute for national criminal justice systems. It may act only when national systems are unwilling or unable genuinely to investigate and prosecute.
Article 17 of the Rome Statute governs admissibility. A case is inadmissible before the ICC if it is being investigated or prosecuted by a state with jurisdiction, unless that state is unwilling or unable genuinely to carry out the investigation or prosecution.
Unwillingness is established where the national proceedings are for the purpose of shielding the person from criminal responsibility, there has been unjustified delay inconsistent with intent to bring the person to justice, or the proceedings are not conducted independently or impartially.
Inability is established where the state has substantially collapsed or its national judicial system is unavailable.
Complementarity serves two purposes. It preserves state sovereignty over domestic criminal justice: states retain primary jurisdiction. It prevents impunity: where states protect perpetrators, the ICC steps in.
U nwillingness: shielding, unjustified delay, lack of independence
U nability: state collapse, judicial system unavailable
A ctivation: ICC may proceed only when national system fails on either ground
Article 27: Irrelevance of Official Capacity
Article 27 of the Rome Statute provides that the Statute applies equally to all persons without any distinction based on official capacity. A head of state, head of government, member of parliament, elected representative, or government official shall in no case exempt a person from criminal responsibility under the Statute.
This directly overrides the head of state immunity that applies under customary international law before domestic courts. The Pinochet case (1999) had already eroded immunity for international crimes before domestic courts. Article 27 eliminates it entirely before the ICC for states parties.
The tension with Article 98 (which prohibits the ICC from requesting surrender in ways that would require the requested state to act inconsistently with its obligations under international law regarding diplomatic or state immunity) has created practical difficulties: the arrest warrant against Omar al-Bashir of Sudan (a non-party) divided opinion on whether states parties were obliged to arrest him on their territory.
ICJ vs ICC: Key Distinctions
| Dimension | ICJ | ICC |
|---|---|---|
| Parties | States only | Individuals only |
| Type of jurisdiction | Civil: interstate disputes and advisory opinions | Criminal: genocide, crimes against humanity, war crimes, aggression |
| Establishment | UN Charter and ICJ Statute, 1945 | Rome Statute, 1998 (in force 2002) |
| Relationship to UN | Principal organ of the UN | Independent organisation; relationship agreement with UN |
| Jurisdiction basis | Consent: special agreement, treaty, optional clause | Territory or nationality of accused; SC referral |
| Complementarity | Not applicable | Yes: court of last resort; national systems have priority |
| Binding force | Judgment binding on parties (Article 59) | Conviction binding on accused |
| Enforcement | Security Council (Article 94 UN Charter) | States parties obligated to cooperate and surrender |
Common Confusions
The ICJ has no compulsory jurisdiction. It can hear a case only if the respondent state has consented. The optional clause system creates compulsory jurisdiction only between states that have both made declarations, and those declarations may contain reservations. A state that has not accepted jurisdiction can simply decline to appear.
The ICC has jurisdiction only over the four Rome Statute crimes and only where the territory or nationality precondition is met or the Security Council refers the situation. It does not have universal jurisdiction. It cannot prosecute crimes in non-party states unless the Security Council refers the situation.
Article 27 eliminates immunity before the ICC for states parties. It does not affect customary international law immunity before domestic courts (as recognised in the Arrest Warrant Case, ICJ 2002). Heads of state of non-party states retain immunity before domestic courts of other states. The ICC context is distinct from domestic court proceedings.
Key Takeaways
ICJ: principal judicial organ of UN. 15 judges. States only. Contentious and advisory jurisdiction. No compulsory jurisdiction: consent required. Four bases: STOF. Judgments binding on parties only (Article 59). Enforcement through Security Council (Article 94).
ICC: Rome Statute 1998. Individuals only. Four crimes: genocide, crimes against humanity, war crimes, aggression. Complementarity: court of last resort (Article 17). Article 27: no immunity for official capacity. Security Council referral extends reach to non-party states.
Memory Hooks: STOF: four bases of ICJ jurisdiction UUA: complementarity triggers ICJ vs ICC table
📋 Facts: Australia and New Zealand brought proceedings against France challenging its programme of atmospheric nuclear tests in the South Pacific. Before the merits were heard, France publicly announced it would cease atmospheric testing.
⚖️ Issue: Whether the ICJ had jurisdiction and whether France's unilateral declaration extinguished the legal dispute.
🏛️ Held: The ICJ held that France's public unilateral declaration to cease testing was legally binding and had removed the subject matter of the dispute. The cases were removed from the list. The court did not decide the merits.
🎯 Significance: Establishes that unilateral declarations by states can create binding legal obligations under international law if made publicly with the intent to be bound. Key authority on the jurisdiction and mootness doctrine of the ICJ.
Full case notes
📋 Facts: Nicaragua brought proceedings alleging that the USA had violated international law by training, arming, and directing Contra rebels and by mining Nicaraguan harbours. The USA contested ICJ jurisdiction and withdrew from the proceedings.
⚖️ Issue: Whether the ICJ had jurisdiction; whether customary international law prohibited the use of force and interference in the internal affairs of another state.
🏛️ Held: The ICJ upheld jurisdiction under the Optional Clause. On the merits, it held that the USA had violated customary international law by using force and interfering in Nicaragua's domestic affairs. The customary law prohibition on the use of force exists independently of the UN Charter.
🎯 Significance: The most important ICJ case on the prohibition of the use of force and non-intervention. Confirms that the ICJ can adjudicate claims against permanent members of the Security Council. Authoritative on the content of customary international law on force and self-defence.
Full case notes
📋 Facts: Thomas Lubanga Dyilo, a Congolese warlord, was charged with the war crime of conscripting and enlisting children under the age of 15 and using them to participate actively in hostilities in the Democratic Republic of the Congo.
⚖️ Issue: Whether conscripting and enlisting children constituted a war crime within the ICC's jurisdiction under Article 8 of the Rome Statute.
🏛️ Held: The ICC Trial Chamber found Lubanga guilty and sentenced him to 14 years' imprisonment. This was the first conviction by the ICC since its establishment in 2002.
🎯 Significance: The first ICC conviction. Establishes the ICC's capacity to hold individuals criminally accountable for war crimes. Landmark authority on the crime of using child soldiers and the ICC's procedural and substantive framework.
Full case notes
Jurisdiction of the International Court of Justice
The International Court of Justice, the principal judicial organ of the United Nations, has jurisdiction over disputes between states and may also give advisory opinions on legal questions. Only states may be parties in contentious proceedings under Article 34 of the ICJ Statute.
The ICJ has no compulsory jurisdiction. A state can be brought before the Court only if it has consented to its jurisdiction. Consent is established in four ways: by special agreement between the parties after the dispute arises; by a treaty clause submitting disputes to the Court; by a unilateral optional clause declaration under Article 36(2), which is reciprocal between declaring states; or by forum prorogatum, where a state implicitly accepts jurisdiction through participation in proceedings.
The Court also exercises advisory jurisdiction under Article 65, giving opinions on legal questions at the request of the General Assembly, the Security Council, or other authorised UN organs. Advisory opinions are not binding but carry substantial legal authority. The ICJ determines its own jurisdiction under the kompetenz-kompetenz principle: preliminary objections to jurisdiction are resolved by the Court itself before proceedings on the merits.
Part A (6 marks)
Complementarity Principle under the Rome Statute
The complementarity principle, codified in Article 17 of the Rome Statute (1998), establishes the International Criminal Court as a court of last resort. The ICC may exercise jurisdiction only when national criminal justice systems are unwilling or unable genuinely to investigate and prosecute the crimes within the Court's jurisdiction.
Unwillingness is established where national proceedings are designed to shield the accused from criminal responsibility, where there is unjustified delay inconsistent with intent to bring the person to justice, or where proceedings lack independence or impartiality. Inability is established where the state has substantially collapsed or its judicial system is unavailable.
Complementarity serves two purposes simultaneously. It preserves the primary role of national jurisdictions over criminal matters, respecting state sovereignty. It prevents impunity: where a state protects perpetrators or cannot function judicially, the ICC's jurisdiction is activated. The principle makes the ICC a safety net for the international criminal justice system, not a replacement for national courts.
Part B (15 marks)
Discuss the Composition, Jurisdiction and Functions of the International Court of Justice / International Criminal Court
- ICJ: principal judicial organ of UN; Statute integral to UN Charter; seated at The Hague
- Composition: 15 judges, 9-year terms, elected by GA + SC concurrently; ad hoc judges available
- ICJ contentious jurisdiction: only states; consent required (STOF: Special agreement, Treaty clause, Optional clause Article 36(2), Forum prorogatum)
- ICJ advisory jurisdiction: GA, SC, and authorised UN organs may request opinions
- Article 38(1): authoritative enumeration of sources of international law
- Enforcement: Article 94 UN Charter; SC action if state fails to comply (subject to veto)
- ICC: established by Rome Statute 1998, in force 2002; international criminal jurisdiction over individuals
- ICC jurisdiction: genocide, crimes against humanity, war crimes, crime of aggression; complementarity with national courts
Case Laws
| Case | Court | Year | Principle |
|---|---|---|---|
| Nuclear Tests Cases (Australia v France) | ICJ | 1974 | Unilateral public declarations by states can be legally binding. ICJ can remove a case as moot where the subject matter of the dispute has been extinguished. |
| Nicaragua v USA (Military and Paramilitary Activities) | ICJ | 1986 | Customary law prohibition on use of force is independent of the UN Charter. ICJ has jurisdiction over permanent Security Council members. Non-intervention is a binding rule of customary international law. |
| Prosecutor v Lubanga Dyilo | ICC | 2012 | First ICC conviction. Conscripting and enlisting child soldiers is a war crime. ICC has jurisdiction over individuals for the most serious international crimes under the Rome Statute. |
The next chapter examines the specialised agencies of the UN: WHO, UNESCO, ILO, IMF, and WTO. Each is a distinct international organisation with its own founding instrument, membership, and mandate, coordinated through ECOSOC within the broader UN system.