The aim of the article is to highlight several issues concerning the customary international law status of a number of international humanitarian law (IHL) treaty provisions that arose during the proceedings of the Eritrea-Ethiopia Claims Commission. Specifically, two key issues will be analyzed, namely the Commission's findings that the Geneva Conventions and some provisions of Additional Protocol I reflected customary international law and that international landmine conventions create only treaty obligations and do not yet reflect customary international law. Also, some more detailed conclusions relating to particular problems, such as the issue of the customary nature of the ICRC’s right to visit prisoners of war and its binding character for non-parties to the Geneva Conventions, will be discussed. The 2005 ICRC Study on Customary International Humanitarian Law and the International Criminal Tribunal for the former Yugoslavia’s jurisprudence will also be included as a point of reference to identify the customary character of certain provisions. The main conclusion is that the Commission has significantly contributed to the emerging consensus regarding the status of certain norms of international humanitarian law as customary norms. Furthermore, it has identified lacunae in the existing standards of humanitarian law and suggested the development of new norms to fill those gaps.