Clarifying Jus Cogens, Erga Omnes and the Place of Third-party Countermeasures in International Law

There is substantial support in literature of the idea that all norms of jus cogens are erga omnes, in that they produce obligations applicable towards all states. However, not all obligations erga omnes invariably flow from a jus cogens characterisation. Indeed, although this is the case, there is no simple criterion by which one can determine the extent of the overlap between jus cogens and erga omnes. This relationship is further complicated by questions relating to the kind of measures that states may be permitted to take in order to protect or ensure compliance with obligations erga omnes, bringing to light, the debates surrounding the concept and the place of third-party countermeasures regarding state responsibility. Against this backdrop, this article will assess the concept of obligations erga omnes, its relationship with jus cogens as well as the legal position and the place of third-party countermeasures in relation to the protection of obligations erga omnes and/or as a way of invoking state responsibility by reacting to breaches of international law obligations with erga omnes status.