¹ Brunnée, Jutta and Toope, Stephen Legitimacy and Legality in International Law (Cambridge: Cambridge University Press, 2010) at 80.CrossRefGoogle Scholar

² Ibid at 24.

³ Ibid at 64.

⁴ Ibid at 63.

⁵ Ibid at 62.

⁶ Ibid at 63.

⁷ Ibid at 26 (paraphrasing Fuller, Lon The Morality of Law, revised edition (New Haven, CT: Yale University Press, 1965) at 39.Google Scholar

⁸ Brunnée and Toope, supra note 1 at 38–39, 352.

⁹ Ibid at 352.

¹⁰ Ibid at 53.

¹¹ Ibid at 29ff.

¹² Ibid at 29–30.

¹³ Ibid at 53.

¹⁴ Ibid at 77.

¹⁵ Ibid at 26–27.

¹⁶ Ibid at 27.

¹⁷ Ibid at 283.

¹⁸ See Koskenniemi, Martti From Apology to Utopia: The Structure of International Legal Argument, reprint with new epilogue (Cambridge: Cambridge University Press, 2005)Google Scholar. Koskenniemi famously explained that each element of custom — that is, practice and opinio juris — can be found only by reference to the other element, making the entire definition of customary international law self-referential and indeterminate.

¹⁹ Jennings, Robert in Cheng, Bin ed, International Law: Teaching and Practice (London: Stevens, 1982) at 5.Google Scholar

²⁰ Brunnée and Toope, supra note 1 at 21.

²¹ Ibid at 352.Brunnée and Toope’s treatment of the term “practice of legality” is depicted as an ongoing project by which shared understandings can be “expanded” and “embedded” in legal practice — a use of the term that recognizes that such a practice is needed through all of the stages of the development of a norm.

²² Ibid at 47. Indeed, Brunnée and Toope see opinio juris as a form of entrenched practice.

²³ Ibid at 6.

²⁴ Ibid at 355.