A peremptory norm (also called jus cogens) is a fundamental principle of international law that is accepted by the international community of states as a norm from which no derogation is permitted. Thought to be so fundamental that it even invalidates rules drawn from treaty or custom, “norms of this character, therefore, cannot be derogated from by the will of the contracting parties."
Article 53 of the Vienna Convention on the Law of Treaties defines jus cogens norms as those that are "accepted and recognized by the international community of states as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent international norm of the same character.” This means that even states objecting to the norm are bound by it, and any treaty or international agreement conflicting with a peremptory norm is void. Among the norms most often mentioned as jus cogens include the international prohibitions on slavery, genocide, piracy, and torture.
