Peremptory in law refers to

a) not open to challenge

b) open to challenge

c) social status

d) none of the above

A peremptory norm (also called jus cogens or ius cogens, Latin for "compelling law") is a fundamental principle of international law which is accepted by the international community of states as a norm from which no derogation is ever permitted.

There is no clear agreement regarding precisely which norms are jus cogens nor how a norm reaches that status, but it is generally accepted that jus cogens includes the prohibition of genocide, maritime piracy, slaving in general (to include slavery as well as the slave trade), torture, and wars of aggression and territorial aggrandizement.