The 11 September attacks and the subsequent US invasion of Afghanistan have raised profound questions about the scope of the right of self-defence in intemationallaw, in particular, to whom it applies. The United States has asserted that it has a right of self-defence against attacks by the AI-Qaeda terrorist organisation. However, this would seem to depart from what might be called the "traditional" interpretation of self-defence, which limits the right to between states. In this view, both the perpetrator and the victim of an "armed attack", which gives rise to a right of self-defence, can only be a state. Yet this view itself has somewhat uncertain foundations, not being spelled out in the main provision on self-defence in the UN Charter and instead derived from a custom which shows some notably inconsistent practice. How, then, should the right of self-defence be considered? Is it reserved only for states, or can it also relate to other actors, such as terrorists, peoples and even individuals?