The right of individual and collective self-defence

Abstract

This chapter examines the concept of self-defence under Article 51 of the United Nations Charter and customary international law. It explores the meaning of the concept of armed attack and addresses the following issues: what conduct qualifies as an armed attack? Who or what can be the object of an armed attack? Under what circumstances can States be said to author an armed attack? Can non-State actors author an armed attack and thus be the target of self-defence action? Can self-defence be engaged to neutralise an armed attack before its violent effects manifest? In this respect, the chapter considers the scope and legality of anticipatory and preventive self-defence in view of contemporary security risks such as terrorism. The chapter also examines the scope of the customary law principles of necessity and proportionality and considers the extent to which they limit the right of self-defence. Next, it focuses on the right of collective self-defence. Finally, it investigates the relationship between the right of self-defence and the Security Council.