Abstract/Summary

Military assistance to a State subjected to an armed attack and seeking the assistance of other States in self-defence is a well-accepted concept in international law. However, once the assisting State facilitates the preparation or commission of any acts violating the law of armed conflict (jus in bello), the question immediately arises of whether and to what extent the assistance provided to States involved in non-international armed conflicts comes within the scope of State responsibility for an internationally wrongful act (IWA). Having displaced the law of State responsibility as the lead regime on how to hold States responsible for their IWAs, this article aims to shed light on the rationale and prospects for effectively holding assisting States responsible for IWAs in non-international armed conflicts. It seeks to answer the questions of when are assisting State responsible for in bello violations during non-international armed conflict, when are assisting States responsible for breaches of conduct attributable to them, when are they responsible for their aid and assistance, and whether and to what extent joint responsibility of the assisting State and acting State would be the case. This will be followed by an assessment of the alleged violations committed in the non-international armed conflict in Syria. The central argument builds on State responsibility under the ILC Draft Articles on State Responsibility (ASR), with a specific focus on grounds for holding military allies responsible for in bello violations committed in conjunction with the acting State during non-international armed conflicts.