The central question of this pioneer work on the responsibility of non-state actors (NSAs) and the consequences thereof, is: To whom are such actors, in particular armed opposition groups and business corporations, accountable for their actions in armed conflict and in peace times? Does responsibility in international law apply to these NSAs qua groups? While much has been written about NSAs’ rights and participation in the global theatre as well as the responsibility of the state and international organisations for wrongful acts by NSAs, scant attention has been paid to questions of NSA organizational responsibility, in spite of their potential to wreak international havoc. This volume offers innovative insights into this unexplored territory by analyzing responsibility questions from both theoretical and empirical perspectives.