CUSTOMARY INTERNATIONAL LAW arbitrators, diplomats, politicians, scholars-invoke these sources selectively and usually tendentiously No one, moreover, agrees about how widespread and uniform state practice must be. In theory the practice is supposed to be general in the sense that all or almost all of the nations of the world engage in it. 14 But it is practically impossible to determine whether 190 or so nations of the world engage in a particular practice. CiL is thus usually based on a highly selective survey of state practice that includes major powers and interested nations I5 Increasingly, courts and scholars sometimes ignore the state practice requirement altogether. 16 For example, they refer to a CL prohibition on torture at the same time that they acknowledge that many nations of the world torture their citizens. 7 It is thus unclear when, and to what degree, the state practice requirement must be satisfied The opinio juris requirement raises more problems. 18 To what does the psychological state refer? How does one identify it? There are no settled answers. Courts and scholars sometimes infer it from the existence of a widespread behavioral regularity. I9 But if opinio Juris can be inferred from behavioral regularities, it is redundant with the requirement of a widespread and uniform state practice, which 111-121(1982-V); Wolkfke, supra note_, at 84; Stephen M. Schwebel, The Effect of Resolutions of the U N. General Assembly on Customary Internationa Law. 1979 Proc. Am. Soc. Intl L. 301 14 See Brownlie, supra note_,at 5-6 15 See Wolfke, supra note_, at 78-79; Jonathan Charney, Universal Inter- national Law, 87 Am. J. Int'l L. 529, 537(1993) 16 See Curtis A. Bradley and Jack L. Goldsmith, Customary International Law as Federal Common Law: A Critique of the Modern Position, 110 Harv. L. Rev 815,839-40(1997) 17 See Filartiga v. Penal-Irala 2d 876. 882(2d Cir. 1980): Bruno Simma Philip Alston, The Sources of Human Rights Custom, Jus Cogens, and General Principles, 12 Austl. Y B Int'l L. 82, 90(1992) 18 ee Thirlway, supra note at 47( The precise definition of the opinio juris, the psychological element in the formation of custom, the philosopher's stone which transmutes the inert mass of accumulated usage into the gold of binding leg rules, has probably caused more academic controversy than all the actual contested claims made by states on the basis of alleged custom, put together. " 19 See Brownlie, supra note_, at 7(citing examples)7 CUSTOMARY INTERNATIONAL LAW arbitrators, diplomats, politicians, scholars—invoke these sources selectively and usually tendentiously. No one, moreover, agrees about how widespread and uniform state practice must be. In theory the practice is supposed to be “general” in the sense that all or almost all of the nations of the world engage in it.14 But it is practically impossible to determine whether 190 or so nations of the world engage in a particular practice. CIL is thus usually based on a highly selective survey of state practice that includes major powers and interested nations.15 Increasingly, courts and scholars sometimes ignore the state practice requirement altogether.16 For example, they refer to a CIL prohibition on torture at the same time that they acknowledge that many nations of the world torture their citizens.17 It is thus unclear when, and to what degree, the state practice requirement must be satisfied. The opinio juris requirement raises more problems.18 To what does the psychological state refer? How does one identify it? There are no settled answers. Courts and scholars sometimes infer it from the existence of a widespread behavioral regularity.19 But if opinio juris can be inferred from behavioral regularities, it is redundant with the requirement of a widespread and uniform state practice, which, 111-121 (1982-V); Wolkfke, supra note __, at 84; Stephen M. Schwebel, The Effect of Resolutions of the U.N. General Assembly on Customary International Law, 1979 Proc. Am. Soc. Int’l L. 301. 14 See Brownlie, supra note __, at 5-6. 15 See Wolfke, supra note __, at 78-79; Jonathan Charney, Universal Inter￾national Law, 87 Am. J. Int’l L. 529, 537 (1993). 16 See Curtis A. Bradley and Jack L. Goldsmith, Customary International Law as Federal Common Law: A Critique of the Modern Position, 110 Harv. L. Rev. 815, 839-40 (1997). 17 See Filartiga v. Penal-Irala, 630 F.2d 876, 882 (2d Cir. 1980); Bruno Simma & Philip Alston, The Sources of Human Rights Law: Custom, Jus Cogens, and General Principles, 12 Austl. Y.B. Int’l L. 82, 90 (1992). 18 See Thirlway, supra note, at 47 (“The precise definition of the opinio juris, the psychological element in the formation of custom, the philosopher’s stone which transmutes the inert mass of accumulated usage into the gold of binding legal rules, has probably caused more academic controversy than all the actual contested claims made by states on the basis of alleged custom, put together.”). 19 See Brownlie, supra note __, at 7 (citing examples)