text is concluding that some norms are proved outside of the state practice/opinio juris paradigm, and should be understood to lower the threshold of evidence of a norm, when the norm would be essential for international coexistence. This conclusion is not so controversial. We can recall that many domestic jurisdictions actually do not rigorously test the two-element rule. The courts of many states will accept (or at least give a presumption of validity to) the determination of the executive on the existence of a rule of customary international law.13 Others may rely on scholarly writing on the subject or even expert testimony as to the content of the law.14 This approach is also not unfamiliar to international tribunals.15 Tribunals might also find a rule of customary international law exists simply due to either party failing to object to it.16 Practice shows a variety of factors that can establish a presumption in favor of a rule of customary international law beyond the coexistence and vital cooperation standard mentioned above. Important bases for a presumption may be when the proposed rule is simply logical or important.17 The rule could be derived logically from other rules or principles,18 it could play an important role in international society,19 or it could uphold certain important values. 20 13 See e.g. R. v. Bottrill, ex parte Kuechenmeister, [1947] 1 K.B. 41 (Ct. Appl., U.K., 1947). See e.g. In re Bouterse (Sup. Ct., Neths., Sept. 18, 2001), reported at 32 NETH. YB INT’L L. 282-96 (2001); Permanent Mission of Ireland to the UN, Decisions of national courts of Ireland relating to the formation and evidence of customary international law (Apr. 1, 2014) available at http://legal.un.org/docs/?path=../ilc/sessions/66/pdfs/english/icil_ireland.pdf&lang=E (citing Gov’t Canada v Employment Appls Trib., [1992] 2 IR 484 (Sup. Ct., Ire., March 12, 1992); ACE Shipping (PTE) Ltd v Min Marine, [1995] 3 IR 406 (High Ct., Ire., Feb 7, 1995; McElhinney v Williams [1995] 3 IR 382 (Sup. Ct., Ire., Dec 15, 1995; Horgan v An Taoiseach [2003] 2 IR 468 (High Ct., Ire., Apr 28, 2003) 15 See Int’l Crim. Ct., Ofc. of the Pros., Situation in Palestine: Summary of submissions on whether the declaration lodged by the Palestinian National Authority meets statutory requirements (May 3, 2010), available at http://www.icccpi.int/NR/rdonlyres/D3C77FA6-9DEE-45B1-ACC0-B41706BB41E5/282852/PALESTINEFINAL201010272.pdf; Case File No. 003/07-09-2009-ECCC-OCIJ, Call for Submissions by the parties in Cases 003 and 004 and Call for Amicus Curiae Briefs (Extraord. Chs. Cts. Cambod., Apr. 19, 2016). 16 See, e.g., Jurisdictional Immunities of the State (Ger. v. It.), Judgment, 2012 ICJ Reps. 99 (Feb. 3) (Germany failing to object to Italy’s characterization that the acts of the German Armed Forces in World War II were unlawful under international law); Certain Questions of Mutual Assistance in Criminal Matters (Djib. v. Fr.), Judgment, 2008 ICJ Reps. 177 (June 4) (both France and Djibouti did not bother to object to the application of the Vienna Convention on the Law of Treaties in the case between them, even though neither state is party to that convention); Case C-366/10, Air Transp. Ass’n of Am., paras. 105-6 (“Nor has the existence of those principles of international law been contested by the Member States, the institutions of the European Union, the Republic of Iceland or the Kingdom of Norway in their written observations or at the hearing … [T]he United Kingdom Government and, to a certain extent, the German Government dispute the existence of such a principle.”). 17 See Jurisdictional Immunities of the State (Ger. v. It.), Judgment, 2012 ICJ Reps. 99, para. 57 (Feb. 3) (“The Court considers that the rule of State immunity occupies an important place in international law and international relations.”); Racke, 1998 E.C.R. para. 50 (citing The Gabčikovo-Nagymaros Project (Hung. v. Slovk.), Judgment, 1997 ICJ Reps. 7, para. 104 (Sept. 25)) (“The importance of that principle has been further underlined by the International Court of Justice, which has held that ‘the stability of treaty relations requires that the plea of fundamental change of circumstances be applied only in exceptional cases.’”); Fisheries Jurisdiction Case (U.K. v. Ice.; Germ. v. Ice.), 1974 ICJ Reps. 3, 175 (July 25)) (“When the stakes are not as high, international decision makers have not been as quick to find restrictive customary rules.”). 18 See Juris. Immunities of the State, 2012 I.C.J. Reps. para. 57 (“[The rule of State immunity] derives from the principle of sovereign equality of States, which, as Article 2, paragraph 1, of the Charter of the United Nations makes clear, is one of the fundamental principles of the international legal order. This principle has to be viewed together with the principle that each State possesses sovereignty over its own territory and that there flows from that sovereignty the jurisdiction of the State over events and persons within that territory. Exceptions to the immunity of the State represent a departure from the principle of sovereign equality. Immunity may represent a departure from the principle of territorial sovereignty and the jurisdiction which flows from it.”); North Sea Continental Shelf (Germ. v. Den.; Germ. v. Neth.), 1969 ICJ Reps. 172, 179 (Feb. 20) (Tanaka, J, diss. op.) (“In the event that the customary law character of the principle of equidistance cannot be proved, there exists another reason which seems more cogent for recognizing this character. That is the deduction of the necessity of this principle from the fundamental concept of the continental shelf.”). 19 See Juris. Imms. of the St. (Ger. v. It.), Judgment, 2012 ICJ Reps. 99, para. 57 (Feb. 3) (“The Court considers that the rule of State immunity occupies an important place in international law and international relations.”); Fish. Juris. Case (UK v. Ice.; Germ. v. Ice.), 1974 ICJ Reps. 3, 175 (July 25); Lotus case, supra note 1 at 25 (“A corollary of the principle of the freedom of the seas is that a ship on the high seas is assimilated to the territory of the State the flag of which it flies, for, just as in its own territory, that State exercises its authority, upon it, and no other State may do so”); Racke v. Hauptzollamt 14 3 Electronic copy available at: https://ssrn.com/abstract=3091912