A. Consent Theories

Most contemporary commentators continue to view jus cogens through the voluntarist prism of state consent. The requirement of state consent is justified on grounds that states are sovereign and autonomous, and therefore states cannot be bound by norms to which they have not consented.^[1] The leading consent-based theory of jus cogens conceives of peremptory norms as customary law that has attained peremptory status through state practice and opinio juris.^[2] The Restatement endorses this position, stating that jus cogens "is now widely accepted ... as a principle of customary international law (albeit of higher status).’^[3] For consent theorists, a custom- based conception of jus cogens bolsters international law's legitimacy by ensuring that states maintain firm control over the generation and evolution of peremptory norms. States, however, rarely (if ever) express an affirmative intent to transform ordinary customary norms into peremptory law, and it is unclear what forms of state practice (if any) would support an inference of implied intent. Indeed, critics of jus cogens are quick to point out that many human rights norms such as the prohibition against torture, which are widely accepted as jus cogens, are also widely violated in practice.^[4] Even if state practice clearly supported recognizing peremptory norms as customary international law, the voluntarist approach is hard-pressed to explain why customary norms would bind persistent objectors or nullify subsequent conflicting treaties. It is difficult, therefore, to dispute the assessment that "calling peremptory norms customary distorts the concept beyond recognition.”^[5]

Some scholars have suggested that the requirement of state consent might be satisfied if a representative supermajority of states accepted an emerging norm as peremptory. The ILC's Commentary to Article 53 appears to be sympathetic to this approach. Peremptory norms need not achieve universal acceptance to create a binding international consensus, the ILC opines; instead, international norms may claim a consensus of "the international community of States as a whole” if a "very large majority” of representative states accept the norms as non-derogable.^[6] Circumventing actual state practice, advocates of this consensus theory typically presume that states signal their consent to peremptory norms through a variety of expressive acts, whether they be unilateral declarations by heads of state, diplomatic correspondence, or the simple failure to register a timely objection to emerging norms. Consensus theory thus envisions a new, autonomous mode of general international law formation—a quasi-customary source that is not beholden to state practice or individualized state consent.^[7]

The primary advantage of consensus theory over other consent-based theories of jus cogens is that it liberates peremptory norms from customary international law's persistent objector rule. Yet to the extent that consensus theory continues to posit state consent as the foundation of jus cogens, it remains vulnerable to the same theoretical quandary that vexes consent-based approaches to jus cogens generally, namely: Why may a supermajority of states impose non-derogable duties on a dissenting minority? And even if states did consent to a consensus-based source of international lawmaking, the consent-based paradigm would be ill-equipped to explain why states that disapprove of emerging peremptory norms in the future could not withdraw their consent at will.^[8] Thus, international consensus is not particularly well-suited to furnish the theoretical underpinnings of jus cogens.

As many consent theorists have recognized, the very concept of jus cogens— peremptory norms that bind states irrespective of state consent—is sharply at odds with the consent-based account of international lawmaking.^[9] If peremptory norms 2001) (“ ‘Customary international law . . . rests on the consent of states.' . . . In contrast, a state is bound by jus cogens norms even if it does not consent to their application.”) (quoting Comm. of U.S. Citizens Living in Nicar. v. Reagan, 859 F.2d 929, 940 (D.C. Cir. 1988)).

are to be taken seriously as a source of international obligation, their imperative force must derive from some principle other than state consent.

• [1] See Gennady M. Danilenko, International Jus Cogens: Issues of Law-Making, 2 Eur. J. Int'lL. 42, 47 (1991); Georg Schwarzenberger, International Jus Cogens?, 43 Tex. L. Rev. 455, 457-60(1965).
• [2] See, e.g., Michael Byers, Conceptualizing the Relationship Between Jus Cogens and Erga OmnesRules, 66 Nordic J. Int'l L. 211, 212 (1997) (arguing "that jus cogens rules are derived from the‘process of customary international law' ”).
• [3] Third Restatement, supra note 4, § 102 n.6.
• [4] See Alexander Orakhelashvili, Peremptory Norms in International Law 113(2006) (asserting that noncompliance with the peremptory norms against military aggression,torture, genocide, and slavery is too widespread to support the custom theory).
• [5] Orakhelashvili, supra note 45, at 114 (summarizing N.G. Onuf & Richard K.Bierney, Peremptory Norms of International Law: Their Source, Function, and Future, 4 DenverJ. Int'l L. & Pol'y 187, 193 (1974)); see also Sampson v. F.R.G., 250 F.3d 1145, 1149 (7th Cir.
• [6] See Third Restatement, supra note 4, § 102 n.6 (citing United Nations Conference on theLaw of Treaties, Mar. 26-May 24, 1968, Report of the Proceedings of the Committee of the Whole,471-72, U.N. Doc. A/CONF.39/11 (May 21, 1968) (comments of the chairman)).
• [7] See W. Michael Reisman, Unilateral Action and the Transformations of the World ConstitutiveProcess: The Special Problem of Humanitarian Intervention, 11 Eur. J. Int'l L. 3, 15 n.29 (2000)("In human rights discourse, jus cogens has . . . evolv[ed] into a type of super-custom, basedon trans-empirical sources and hence not requiring demonstration of practice as proof of itsvalidity.”).
• [8] See Jerzy Sztucki, Jus Cogens and the Vienna Convention on the Law ofTreaties: A Critical Reappraisal 97 (1974).
• [9] See id. at 64 (“[T]he introduction of a consensual ingredient into the concept of jus cogensleads inevitably, in the ultimate instance, to the very negation of that concept.”); see Sidermanv. Republic ofArgentina, 965 F.2d 699 (9th Cir. 1992) (stating that jus cogens norms “transcendconsent”).