The prohibition of the use of force is generally considered to be a jus cogens rule, which would mean that it does not permit any derogation, neither by consent nor by treaty. Yet multiple apparent derogations from the prohibition exist: Articles 42 and 51 of the UN Charter, Articles 105, 110 and 111 of the UNCLOS, and other treaties all permit uses of force, and ad hoc consent to use force is common. This article explains how this can be legally valid, by reference to the distinctions between derogations, exceptions, and scope.