Legality of the threat of use of nuclear weapons. ICJ Advisory Opinion of 8 July 1996

In December 1994, the United Nations General Assembly requested the International Court of Justice (ICJ) to provide an advisory opinion on the legality of the threat or use of nuclear weapons under international law. The Court received written statements from 28 states and oral statements from 22 states during the proceedings.

In its Advisory Opinion rendered on July 8, 1996, the ICJ determined that it had jurisdiction to provide an opinion on the matter and found that the relevant applicable law included the United Nations Charter provisions on the use of force and the law applicable in armed conflict. The Court emphasized that the principles and rules of humanitarian law were essential in evaluating the legality of using force, including nuclear weapons.

The Court clarified that the principle of proportionality might not always exclude the use of nuclear weapons in self-defense, but any use of force, including nuclear weapons, must comply with the requirements of humanitarian law. It stressed that the notions of the "threat" and "use" of force were interlinked, meaning that if the use of force was illegal, the threat to use such force would also be illegal.

The ICJ examined customary and conventional international law and concluded that there was no specific prohibition of nuclear weapons based on those sources. It also found that the emergence of a customary rule specifically prohibiting the use of nuclear weapons was hindered by differing opinions within the international community.

Regarding the principles and rules of humanitarian law, the Court emphasized two key principles: the distinction between combatants and non-combatants, and the avoidance of unnecessary suffering to combatants. States were not free to choose weapons without limitations, as they must not target civilians and must use weapons capable of distinguishing between civilian and military targets.

The Court acknowledged the controversy surrounding the conclusions drawn from the application of humanitarian law to nuclear weapons due to their unique characteristics. It stated that it could not definitively conclude whether the threat or use of nuclear weapons would be lawful or unlawful in extreme circumstances of self-defense where the survival of a state was at stake.

The ICJ also recognized an obligation for states to engage in good faith negotiations leading to nuclear disarmament, with strict and effective international control.