AMBIGUITIES REGARDING THE NECESSITY AND PROPORTIONALITY CRITERIA FOR THE EXERCISE OF SELF-DEFENCE IN INTERNATIONAL LAW

The precise scope of the right of self-defence remains a very controversial aspect of jus ad bellum; this has led to fundamental divisions among states and international law scholars. This thesis examines possible ambiguities in the interpretation of the necessity and proportionality requirements as criteria for lawful self-defence, and the extent to which recent state practice has adjusted the scope of these criteria. It also considers the armed attack criterion to the extent necessary to shed light on the criteria of necessity and proportionality. This thesis argues that, while ambiguities remain in relation to specific aspects of the necessity and proportionality standards, the contours of these standards are relatively well-defined under the contemporary international legal rules governing defensive action. This means that the areas of ambiguities concerning the scope of these dual conditions of defensive force are considerably narrower than the assessment of the divergent commentary indicates. This thesis also argues that the criteria of necessity and proportionality, as they now stand, are very restrictive in nature, and recent state practice does not suggest that their scope has been so widened as to include expansive self-defence measures such as action against unattributable attacks by non-state actors and preventive use of force. In contrast, recent attempts to expand the scope of the necessity and proportionality criteria, such as the US’s drone program outside Afghanistan and the ongoing American-led air campaign in Syria, can be seen as a violation of these criteria, given the lack of opinio juris confirming that such attempts have been endorsed by ‘the international community of state as a whole’. This thesis also argues that the extent and strength of today’s international terrorism would require that the intervening states engage in prolonged self-defence operations against non-state armed groups, attacking them in several foreign states (that are mostly judged to be unwilling or unable to halt the non-state groups’ actions) for quite a long time. This not only will lead to a breach of the temporal and geographical criteria for proportionate self-defence, but may give rise to a possible violation of the ‘legitimate target’ criterion for jus ad bellum necessity. This thesis thus argues that states are well advised to take a clear legal stance against any broad interpretations of necessity and proportionality (such the ‘unwilling or unable’ test) that justifies acting in self-defence against unattributable attacks from non-state armed groups.