This article examines the requirement under international humanitarian law (IHL) that consent to humanitarian relief operations must not be arbitrarily withheld. It begins with a brief outline of the rules of IHL regulating humanitarian assistance in armed conflict. The article then considers the origin of the rule prohibiting arbitrary withholding of consent to humanitarian relief operations before proceeding to set out the circumstances when consent will be considered to have been withheld arbitrarily under international law. It proposes three tests for arbitrariness in this context, and also examines how international human rights regulates humanitarian assistance in armed conflict