2021] NATIONALITY LAWS 135 matter in present-day international law which appears to be a successful candidate for regulation by peremptory norms, it is certainly the prohibition of racial discrimination.”229 Referring to both Schwelb and Brownlie, Warwick McKean reasoned in 1983 that if genocide and slavery, as “extreme forms” of the denial of the principle of equality are considered to possess a jus cogens character, then “it is not unreasonable to suppose that other examples of the denial of the principle [of equality] may be contrary to the doctrine” and that non-discrimination “is a strong candidate for inclusion under this heading.” 230 Other scholars have framed the jus cogens norm as relating to severe or systemic forms of racial discrimination. Lauri Hannikainen writes that the jus cogens prohibition applies to “severe” forms of discrimination, adding that the prohibition may further extend to “substantial” acts of discrimination which affect the non- piracy, other crimes against humanity, and the principles of self-determination. Id. at 417. 229 Egon Schwelb, Some Aspects of International Jus Cogens as Formulated by the International Law Commission, 61 AM. J. INT’L L. 946, 956 (1976). 230 WARWICK MCKEAN, EQUALITY AND DISCRIMINATION UNDER INTERNATIONAL LAW 277–84 (1983). See also AUSTIN, supra note 212, at 10 (“There is no agreement on the criteria for identifying which principles of general international law have a peremptory character: everything depends on the particular nature of the subject matter. Perhaps the only generally accepted examples of jus cogens are the prohibitions on the use of force (as laid down in the UN Charter) and on aggression, genocide, slavery, racial discrimination, torture and crimes against humanity.”); LERNER, GROUP RIGHTS AND DISCRIMINATION IN INTERNATIONAL LAW, supra note 212, at 24, 71 (noting that racial discrimination at least is already considered a jus cogens, namely a peremptory rule of international law from which no derogation is possible, a rule that can only be modified by a new rule of the same status. “However, as stated by the UN Secretary General in a report on the implementation of the program of action for the Second Decade to Combat Racism and Racial Discrimination, the Convention is endowed ‘with strong moral force of virtually universality rooted in the overriding principle (jus cogens) that racial discrimination must be eliminated everywhere.’”); VAN DERVORT, supra note 212, at 408 (stating that the concept of jus cogens is still subject to some controversy but would generally include the prohibition of the use or threat of force and aggression and the prevention and repression of genocide, piracy, slave trade, racial discrimination, terrorism or the taking of hostages, and torture, even though the evolving nature of these principles does not allow a conclusive definition); JOHN TOBIN, THE U.N. CONVENTION ON THE RIGHTS OF THE CHILD: A COMMENTARY 42 (2019) (citing LOUIS HENKIN, THE INTERNATIONAL BILL OF RIGHTS: THE COVENANT ON CIVIL AND POLITICAL RIGHTS 249 (1983)).