The legality of the air strikes against ISIL in Syria: new insights on the extraterritorial use of force against non-state actors

The extraterritorial use of force by a state against non-state actors has been a contentious issue in international law since 9/11 and the adoption of UN Security Council Resolutions 1368 and 1373. The current air strikes against ISIL in Syria are playing a major role in the development of the international debate surrounding the legality of such extraterritorial strikes. This article seeks to analyse the various justifications for the legality of the use of force against ISIL in Syria, and whether such justifications have caused a shift in the current legal framework. In particular, it discusses four potential legal justifications for the air strikes in Syria: the consent of the territorial state, the applicability of the traditional right to self-defence, the crystallisation of the ‘unwilling or unable’ test, and the development of a new sui generis doctrine on the use of force against non-state actors. In the absence of an appropriate legal justification, the last section of this article examines whether the international community is overlooking the unlawfulness of the air strikes, in the interest of international security.