Abstract This article examines whether states may use force in self-defence against non-state actors operating from the territory of another state. It first maps the prevailing approaches to self-defence in response to non-state armed attacks, focusing on attribution, Article 3(g) of the United Nations General Assembly’s Definition of Aggression, and the ‘unable or unwilling’ doctrine. It argues that these approaches give rise to normative, methodological and practical difficulties and often leave states without an effective right to defend themselves. The article then goes on to explain the morphology of the right of self-defence. It contends that self-defence is a primary rule of international law permitting the use of force in response to an armed attack as a factual occurrence, irrespective of its perpetrator. It further argues that self-defence is neither an exception to Article 2(4), nor a legal sanction. On this basis, the right of self-defence extends to armed attacks by non-state actors, even when they operate from within the territory of another state. In such cases, self-defence as a circumstance precluding wrongfulness excuses the responsibility of the defending state for incidental violations of the territorial state’s sovereignty in the course of defensive action.
Nicholas Tsagourias (Thu,) studied this question.