Jus Cogens implies the body of preemptory principles or norms from which no derogation is allowed. Any treaty or agreement which is inconsistent with these principles is invalid up to the extent of such inconsistency. As mentioned in Art. 53 of the Vienna convention on the Law of Treaties of 23 May 1969, norm of jus cogens can be modified only by a subsequent norm of general Interna­tional law.