...as originally understood, article 51 did not permit
extraterritorial force against non-state actors without the consent of the territorial State. The real question, therefore, is whether state practice, whether as a constituent element of customary international law, or as subsequent practice for the purposes of interpreting the UN Charter, could have modified this original state-centric reading of the Charter. This question is at the heart of a forthcoming book, The Trialogue on the Use of Force against Non-State Actors (Mary Ellen O’Connell, Christian Tams, Dire Tladi). In my view, an...