term:

Jus Cogens

jus cogens n

[New Latin, literally, constraining law]
: a principle of international law that is based on values taken to be fundamental to the international community and that cannot be set aside (as by treaty) [it is doubtful that any state has ever violated jus cogens norms on a scale rivaling that of the Third Reich "Princz v. Federal Republic of Germany, 26 F.3d 1166 (1994)"] [genocide and slave trade are violations of jus cogens]

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.