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World Court Digest

I. Substantive International Law - First Part
6.1. Use of Force

¤ Legality of the Threat or Use
of Nuclear Weapons
Advisory Opinion of 8 July 1996
I.C.J. Reports 1996, p. 226

[p. 244] 37. The Court will now address the question of the legality or illegality of recourse to nuclear weapons in the light of the provisions of the Charter relating to the threat or use of force.

38. The Charter contains several provisions relating to the threat and use of force. In Article 2, paragraph 4, the threat or use of force against the territorial integrity or political independence of another State or in any other manner inconsistent with the purposes of the United Nations is prohibited. That paragraph provides:

"All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the Purposes of the United Nations."

This prohibition of the use of force is to be considered in the light of other relevant provisions of the Charter. In Article 51, the Charter recognizes the inherent right of individual or collective self-defense if an armed attack occurs. A further lawful use of force is envisaged in Article 42, whereby the Security Council may take military enforcement measures in conformity with Chapter VII of the Charter.
39. These provisions do not refer to specific weapons. They apply to any use of force, regardless of the weapons employed. The Charter neither expressly prohibits, nor permits, the use of any specific weapon, including nuclear weapons. A weapon that is already unlawful per se, whether by treaty or custom, does not become lawful by reason of its being used for a legitimate purpose under the Charter.

[pp. 246-247] 46. Certain States asserted that the use of nuclear weapons in the conduct of reprisals would be lawful. The Court does not have to examine, in this context, the question of armed reprisals in time of peace, which are considered to be unlawful. Nor does it have to pronounce on the question of belligerent reprisals save to observe that in any case any right of recourse to such reprisals would, like self-defense, be governed inter alia he principle of proportionality.
47. In order to lessen or eliminate the risk of unlawful attack, States sometimes signal that they possess certain weapons to use in self-defense against any State violating their territorial integrity or political independence. Whether a signalled intention to use force if certain events occur is or is not a "threat" within Article 2, paragraph 4, of the Charter depends upon various factors. If the envisaged use of force is itself unlawful, the stated readiness to use it would be a threat prohibited under Article 2, paragraph 4. Thus it would be illegal for a State to threaten force to secure territory from another State, or to cause it to follow or not follow certain political or economic paths. The notions of "threat" and "use" of force under Article 2, paragraph 4, of the Charter stand together in the sense that if the use of force itself in a given case is illegal - for whatever reason - the threat to use such force will likewise be illegal. In short, if it is to be lawful, the declared readiness of a State to use force must be a use of force that is in conformity with the Charter. For the rest, no State - whether or not it defended the policy of deterrence - suggested to the Court that it would be lawful to threaten to use force if the use of force contemplated would be illegal.

48. Some States put forward the argument that possession of nuclear weapons is itself an unlawful threat to use force. Possession of nuclear weapons may indeed justify an inference of preparedness to use them. In order to be effective, the policy of deterrence, by which those States possessing or under the umbrella of nuclear weapons seek to discourage military aggression by demonstrating that it will serve no purpose, necessitates that the intention to use nuclear weapons be credible. Whether this is a "threat" contrary to Article 2, paragraph 4, depends upon whether the particular use of force envisaged would be directed against the territorial integrity or political independence of a State, or against the Purposes of the United Nations or whether, in the event that it were intended as a means of defense, it would necessarily violate the principles of necessity and proportionality. In any of these circumstances the use of force, and the threat to use it, would be unlawful under the law of the Charter.