## Facts

- The United Nations General Assembly requested an advisory opinion asking whether the threat or use of nuclear weapons is permitted under international law in any circumstance.
- The International Court of Justice received written submissions from numerous states and held oral hearings before issuing its advisory opinion.
- The Court treated the request as raising a legal question concerning the U.N. Charter rules on force, the law of armed conflict (international humanitarian law), and relevant treaty obligations concerning nuclear weapons and disarmament.

## Issues

1. Whether the Court had jurisdiction to render, and should render, an advisory opinion on the legality of the threat or use of nuclear weapons.
2. Whether international law contains a specific authorization or a comprehensive and universal prohibition of the threat or use of nuclear weapons as such.
3. Whether a threat or use of nuclear weapons is unlawful when inconsistent with U.N. Charter limits on force, including the rules governing self-defense.
4. Whether any use of nuclear weapons, even if otherwise justified under self-defense, must comply with international humanitarian law rules governing conduct of hostilities.
5. Whether the Court could determine legality in an extreme circumstance of self-defense in which the survival of a state is at stake.
6. Whether states are legally obligated to pursue and conclude negotiations leading to nuclear disarmament.

## Decision

- The Court held it had jurisdiction to respond to the General Assembly’s request and found no compelling reason to decline to answer.
- The Court found no specific authorization in international law for the threat or use of nuclear weapons, and no comprehensive and universal prohibition of nuclear weapons as such in treaty law or customary international law.
- The Court held that any threat or use of nuclear weapons must comply with the U.N. Charter; if the contemplated use of force would be unlawful, the threat to use that force is likewise unlawful.
- The Court held that even when force is permitted under self-defense, the threat or use of nuclear weapons must also satisfy international humanitarian law, including distinction, proportionality, and the prohibition on unnecessary suffering.
- The Court concluded that the threat or use of nuclear weapons would generally be contrary to international humanitarian law, but it could not reach a definitive conclusion on legality or illegality in an extreme circumstance of self-defense where a state’s survival is at stake.
- The Court unanimously concluded that states have an obligation to pursue in good faith and bring to a conclusion negotiations leading to nuclear disarmament under strict and effective international control.

## Legal Principles

- Advisory jurisdiction extends to legal questions posed by the U.N. General Assembly; political sensitivity alone is not a sufficient reason to refuse an advisory opinion.
- The U.N. Charter’s prohibition on force and the right of self-defense apply regardless of weapon type; nuclear weapons are not exempt from Charter constraints.
- Threat and use of force are legally linked: a threat is unlawful if the envisaged use would be unlawful under applicable law.
- Lawful self-defense under the Charter (including necessity and proportionality) does not displace international humanitarian law; conduct of hostilities must independently satisfy IHL limits.
- Core IHL rules governing means and methods of warfare include distinction, proportionality, and the ban on weapons or methods causing superfluous injury or unnecessary suffering; nuclear weapons’ effects make compliance generally unlikely.
- In the absence of clear, universal treaty text or sufficiently consistent state practice and opinio juris, the Court would not declare a categorical customary prohibition on nuclear weapons in all circumstances.
- States are obligated to negotiate in good faith toward complete nuclear disarmament under strict and effective international control.

## Conclusion

The Court held that nuclear threats and uses are governed by the U.N. Charter and international humanitarian law, found no universal rule categorically authorizing or banning nuclear weapons as such, concluded such use would generally violate IHL, declined to decide legality in an extreme self-defense scenario threatening state survival, and unanimously recognized a duty to pursue and conclude negotiations toward nuclear disarmament.


Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. 226 (July 8)