Self-defense

In the seventeenth century, Hugo Grotius identified defense as one of the three categories of just causes for war. This notion of defense was not confined to the actual fending off of an ongoing attack, but extended to the taking of action against impending dangers as well. There were naturally some worries over the potential misuse of this right of defensive war, and international lawyers were at pains to stress that it could not be used to justify action against dangers that were merely speculative. In the nineteenth century, the idea of self-defense played little role in international legal discourse because of the general acceptance of war as an inherent sovereign right of states. When lawyers wrote of emergency action by states, they generally spoke instead in terms of a more general right of self-preservation (or, in modern terminology, necessity), which would justify states in taking emergency action that normally would be unlawful. The criteria for the exercise of this right of necessity were most memorably articulated by American secretary of state Daniel Webster, in 1841: when there is “a necessity , instant, over whelming, leaving no choice of means, and no moment for deliberation.” This statement by Webster has been adopted by international lawyers as the basic standard for self-defense. Self-defense was not expressly mentioned in the text of the Kellogg–Briand Pact of 1928. Nevertheless, it was clear from the context that the states parties recognized that it was outside the scope of the prohibition against war. Only in 1945, with the conclusion of the United Nations Charter, did self-defense move to the legal center stage. The Charter allows self-defense in case of “armed attack” (Article 51) — the only important circumstance in which states may employ armed force unilaterally.

Keywords: law; preemption; punitive action; reprisals; rights; war