A peremptory norm (also called jus cogens or ius cogens /ˌdʒʌs ˈkoʊdʒɛnz/ or /ˌjʌs/; Latin for "compelling law") 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.
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, non-refoulement and wars of aggression and territorial aggrandizement. Recent scholarship has also proposed the idea of a regional jus cogens.
Status of peremptory norms under international law
Unlike ordinary customary law, which has traditionally required consent and allows the alteration of its obligations between states through treaties, peremptory norms cannot be violated by any state "through international treaties or local or special customs or even general customary rules not endowed with the same normative force".
Discussions of the necessity of such norms could be traced as far as 1758 (Emmerich de Vattel, Droit des gens) and 1764 (Christian Wolff, Jus Gentium), clearly rooting from principles of natural law.
But it was the judgments of the Permanent Court of International Justice that indicate the existence of such a peremptory norm. In the Wimbeldon Case in 1923, not mentioning peremptory norms explicitly but stating how state sovereignty is not inalienable.
Under Article 53 of the Vienna Convention on the Law of Treaties, any treaty that conflicts with a peremptory norm is void. The treaty allows for the emergence of new peremptory norms, but does not specify any peremptory norms. It does mention the prohibition on the threat of use of force and on the use of coercion to conclude an agreement:
"A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law. For the purposes of the present Convention, a peremptory norm of general international law is a norm 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 norm of general international law having the same character."
The number of peremptory norms is considered limited but not exclusively catalogued. They are not listed or defined by any authoritative body, but arise out of case law and changing social and political attitudes. Generally included are prohibitions on waging aggressive war, crimes against humanity, war crimes, maritime piracy, genocide, apartheid, slavery, torture. As an example, international tribunals have held that it is impermissible for a state to acquire territory through war.
Despite the seemingly clear weight of condemnation of such practices, some critics disagree with the division of international legal norms into a hierarchy. There is also disagreement over how such norms are recognized or established. The relatively new concept of peremptory norms seems to be at odds with the traditionally consensual nature of international law considered necessary to state sovereignty.
Some peremptory norms define criminal offences considered to be enforceable against not only states but also individuals. That has been increasingly accepted since the Nuremberg Trials (the first enforcement in world history of international norms upon individuals) and now might be considered uncontroversial. However, the language of peremptory norms was not used in connection with these trials, rather the basis of criminalisation and punishment of Nazi atrocities, was that civilisation could not tolerate their being ignored because it could not survive their being repeated.
There are often disagreements over whether a particular case violates a peremptory norm. As in other areas of law, states generally reserve the right to interpret the concept for themselves.
Many large states have accepted this concept. Some of them have ratified the Vienna Convention, while others have stated in their official statements that they accept the Vienna Convention as "codificatory". Some have applied the concept in their dealings with international organizations and other States.
2) M. Cherif Bassiouni. (Autumn 1996) "International Crimes: 'Jus Cogens' and 'Obligatio Erga Omnes'." Law and Contemporary Problems. Vol. 59, No. 4, Pg. 68.
3) Hasmath, Reza (2012). "The Utility of Regional Jus Cogens", Paper Presented at American Political Science Association Annual Meeting (New Orleans, USA), August 30-September 2.
4) Prosecutor v. Furundzija, International Criminal Tribunal for the Former Yugoslavia, 2002, 121 International Law Reports 213 (2002)
5) Władysław Czapliński. Jus Cogens and the Law of Treaties. In C. Tomuschat and J. M. Thouvenin (eds). 2006. The Fundamental Rules of the International Legal Order. Netherlands: Koninklijke Brill NV, pp. 83–98
6) Cherif Bassiouni. 2011. Crimes Against Humanity: Historical Evolution and Contemporary Application. New York: Cambridge University Press, p. 266, see also Wimbledon Case, p.25
7) Vienna Convention on the Law of Treaties, Article 53, May 23, 1969, 1155 U.N.T.S 331, 8 International Legal Materials 679 (1969)
8) Vienna Convention on the Law of Treaties, Article 64, May 23, 1969, 1155 U.N.T.S 331, 8 International Legal Materials 679 (1969)
9) U.N. Doc. A/CONF.39/27 (1969), repinted in 63 Am. J. Int'l L. 875 (1969).
10) Marc Bossuyt en Jan Wouters (2005): Grondlijnen van internationaal recht, Intersentia, Antwerpen enz., p. 92.
11) Prosecutor v. Furundžija, International Criminal Tribunal for the Former Yugoslavia, 2002, 121 International Law Reports 213 (2002)