Art.51 says that “Nothing in the present charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of United Nations until the Security Council has taken measures necessary to maintain international peace and security.” Let us examine some cases which define the international Law standard for whether a particular use of force in self-defense.
An American ship, The Caroline in a US port. because Caroline had been used in American raids into Canadian territory. The British claimed the attack was self-defense. But the dispute was resolved in favor of Americans.
This particular case had given a clear meaning to the term self-defense under International Law as “there must be a necessity of self-defense- instant, overwhelming, leaving no choice of means and no choice of means and no moment for deliberation.” The means of self-defense must involve nothing unreasonable or excessive: Since the act, justified by the necessity of self-defense, must be limited by that necessity, and kept clearly within it. This has been accepted rule in International Law. This is somewhat called “anticipatory Self-defense”.
This case heard in 1986 by the International Court Of Justice and found that the US had violated International Law by providing weapons, finance and other logical assistance to guerilla forces who carried out the ongoing attack against both Nicaraguan armed forces and civilians in Nicaragua.*
Arming and training the contra guerillas was found to be in breach with principles of nonintervention and prohibition of the use of force. .