The Exercise of Self-Defence Against ISIL in Syria: New Insights on the Extraterritorial Use of Force Against Non-State Actors

Abstract

The extraterritorial use of force by a State against non-State actors has been a contentious issue in international law in modern times. In past cases where States have invoked self-defence to justify such attacks, the international community has been quick to condemn them as violations of the sovereignty and territorial integrity of the State on whose territory such attacks take place. In contrast, the current air strikes against ISIL in Syria – carried out by an international coalition in collective self-defence of Iraq – have been met with no such condemnations. Indeed, many more States appear to favour these attacks than in previous comparable cases and very few have protested on the basis of sovereignty concerns. This article seeks to analyse the reasons behind this apparent shift in State practice, and what impact it may have, if any, on the development of the law on the use of force. In particular, it discusses three potential legal justifications for the air strikes, which may underlie the condoning reactions by States: the consent of the territorial State, the crystallization of the ‘Unwilling or Unable’ test and the development of a new legal doctrine on the use of force against non-State actors.

Keywords: jus ad bellum, use of force, self-defence, extraterritorial, ISIL, non-State actors, Syria, Iraq, consent, ‘unwilling or unable’ test