In recent years, the increasingly frequent and, in certain contexts, extremely severe impediments to the provision of humanitarian assistance to civilians in need have focused attention on how to enhance compliance with the rules of international humanitarian law (IHL) that regulate humanitarian relief operations. Efforts to hold accountable parties to armed conflict and persons responsible for unlawfully impeding humanitarian relief operations face the challenge that the underlying rules give parties latitude in how to implement the central obligation to allow and facilitate the rapid and unimpeded passage of humanitarian supplies, equipment and personnel. This article outlines the rules of IHL regulating humanitarian relief operations and highlights the difficulties, in the majority of situations, of determining whether they have been violated. It then presents current endeavours to promote accountability. It concludes with some reflections on whether the threat of accountability is the most effective way of enhancing compliance with this area of IHL, at least while efforts are under way to negotiate access.