Jus cogens (from Latin: compelling law; English: peremptory norm) refers to certain fundamental, overriding principles of international law, from which no derogation is ever permitted. See Ian Brownlie, Principles of Public International Law (5th ed., Oxford, 1998). In practice, jurists' attempt to classify certain rules, rights and duties as jus cogens or peremptory norms have not met with success: while there is near-universal agreement for the existence of the category of jus cogens norms, there is far less agreement regarding the actual content of this category. Id. at 517.
Examples of jus cogens norms include: prohibition on the use of force; the law of genocide; principle of racial non-discrimination; crimes against humanity; and the rules prohibiting trade in slaves or human trafficking.