ABSTRACT
In customary international law it was well recognised that the state might employ force in self-defence. Provided a state acted within the formulation in the Caroline case,25 there could be no objection. In that case, British citizens seized and destroyed a vessel in an American port. This action had taken place because it was believed that the Caroline26 was supplying American nationals who had been mounting operations in Canadian territory. In subsequent correspondence with the United Kingdom Government, the Secretary of State Daniel Webster27 argued that any action in self-defence must meet the test of necessity and proportionality. For the situation to be one of self-defence, there must be evidence of ‘a necessity of self-defence, instant, overwhelming, leaving no choice of means and no moment for deliberation’. In respect of the response, Webster argued that it should be proportionate ‘since the act, justified by the necessity of self-defence must be limited by that necessity and kept clearly within it’. The principle of self-defence had been acknowledged from the time of Aquinas, but the virtue of the Caroline test was that it set out certain criteria by which it could be determined whether there had been a legitimate exercise of the right; the test stressed that the action must be necessary and the means employed proportionate. The test was accepted by the United Kingdom and came to be accepted as part of customary international law. The test was referred to in the Nuremberg War Trials and in the Security Council debates on the Cuban Missile Crisis (1962), the Middle East War (1967) and the bombing of the Osarik Nuclear Reactor (1981).
