B. Natural Law Theories
One response to the inadequacy of positivist theories of jus cogens has been to embrace peremptory norms as remnants of the natural law tradition. Prominent human rights theorists such as Louis Henkin and Louis Sohn have suggested that jus cogens norms such as the prohibitions against slavery and military aggression derive their peremptory character from their inherent rational and moral authority rather than state consent; as such, treaties, custom, and general principles might recognize and incorporate peremptory norms, but they could not abrogate them. Similar affirmations of jus cogens as natural law may be distilled from the jurisprudence of the ICJ and the Inter-American Commission on Human Rights. Although few international lawyers today share Vattel's confidence in a universal natural law of reason, many nonetheless agree that “[t]he character of certain norms makes it difficult to portray them as other than peremptory.”
The conceptual challenges associated with natural law theory are well- documented. Although some peremptory norms such as the prohibitions against genocide and slavery are relatively uncontroversial, it is by no means clear how natural law theory would resolve disputes over the scope or content of less well-defined norms, such as the prohibition against torture, once jus cogens is uncoupled from state consent. More troubling still, natural law theory, like consent theory, struggles to explain how peremptory norms can place substantive limits on state action without eviscerating the concept of state sovereignty. For these and other reasons, most international courts and publicists of the last half-century have eschewed reliance on natural law in favor of other theories of jus cogens.
-  Louis Henkin, The International Bill of Rights: The Covenant on Civil andPolitical Rights 15 (1981); Louis B. Sohn, The New International Law: Protection of the Rightsof Individuals Rather than States, 32 Am. U. L. Rev. 1 (1982) (citing the “natural law concept ofrights, rights to which all human beings have been entitled since time immemorial and to whichthey will continue to be entitled as long as humanity survives”).
-  Nicaragua, 1986 ICJ Rep. at 112 (describing certain norms of international humanitarianlaw as “elementary considerations of humanity” that “constitute intransgressible principles”).
-  See, e.g., Michael Domingues v. United States, Case 12.285, Inter-Am. C.H.R., ReportNo. 62/02, OEA/Ser.L/V/II.117, doc. 5 rev.1 ^ 49 (2003), http://www.cidh.org/annualrep/2002eng/USA.12285.htm (describing jus cogens as a “superior order of legal norms, which thelaws of man or nations may not contravene[,] . . . rules which have been accepted . . . as beingnecessary to protect the public morality recognized by them”) (internal citation and quotationmarks omitted).
-  Orakhelashvili, supra note 45, at 108.
-  See Anthony D'Amato, Human Rights as Part of Customary International Law: A Pleafor Change of Paradigms, 25 Ga. J. Int'l & Comp. L. 47, 63-75 (1995-1996) (discussing thistension).