THE PRESUMPTION OF CUSTOMARY INTERNATIONAL LAW: A CASE STUDY OF CHILD STATELESSNESS William Thomas Worster* I. Introduction Child statelessness continues to be a global problem that evades easy solutions and demands better legal solutions. Although UNCHR and other bodies have had some success in increasing participation to the 1954 and 1961 Statelessness Conventions during the current multi-year project to eradicate child statelessness, but if states refuse to adhere to those conventions, it would also be helpful to know if there are any rules of customary international law on child statelessness. Historically, most authorities were reluctant to find that norms existed under customary international law governing child statelessness. However, as practice on child statelessness has developed, so too has practice on customary international law. As a first step in studying whether there are any norms of customary international law on this topic, we will first examine whether there are any presumptions in establishing norms, that can be helpful in assessing the developing practice. Proving when certain norms have emerged in customary international law is also problem that evades easy solutions. However, the International Law Commission (ILC) is finalizing a study on the methodology of customary international law, inspiring a wave of interest in the question in the scholarship. One stumbling block in this study is agreeing on how to assess evidence of customary international law, to determine when the threshold of practice has been met. This author has attempted to identify tools for determining thresholds in the past, but one device for analyzing a threshold question is whether there are any relevant presumptions. Some authors have opined that a presumption exists in favor of a norm of customary international law in certain circumstances. This paper will undertake a preliminary case study on customary international law rules governing child statelessness, specifically considering whether there is a presumption in favor of rules on point. Firstly, it will examine the literature and practice applying a presumption in the customary international law methodology. This question will consider several different factors that might trigger a presumption. Secondly, having concluded that a presumption arises in certain situations, the paper will conduct a case study on applying the presumption by gathering and assessing evidence of relevant situations that would result in a presumption in favor of norms governing child statelessness. II. Presumption of customary international law It is well known that a widespread and consistent state practice and opinio juris will evidence the existence of customary international law.12 The ILC and other authorities have consistently reaffirmed * Senior Lecturer, International Law, The Hague University of Applied Sciences, The Hague, The Netherlands; Ph.D. candidate in International Law, University of Amsterdam, Amsterdam, The Netherlands; LL.M. (Adv.) in Public International Law, cum laude, Leiden University, Leiden, The Netherlands; J.D., Chicago-Kent College of Law, Illinois Institute of Technology, Chicago, Illinois. 1 See Statute of the International Court of Justice art. 38, June 26, 1945, 59 Stat. 1055, 33 U.N.T.S. 993; Statute of the Permanent Court of Justice, Dec. 16, 1920; S.S. “Lotus” (Fr. v. Turk.), 1927 P.C.I.J. (ser. A) No. 10, at 18 (Sept. 7); Asylum case (Colom. v. Peru), Judgment, 1950 I.C.J. 266, 276-77 (Nov. 20); N. Sea Cont. Shelf (Ger. v. Den.; Ger. v. Neth.), Judgment, 1969 I.C.J. 3, 44 (Feb. 20); Mil. & Paramil. Acts. in & ag. Nicar. (Nicar. v U.S.) (Nicaragua case), Judgment, 1986 ICJ 14, para. 207 (June 27); Gregory Shaffer & Tom Ginsburg, The Empirical Turn in International Legal Scholarship, 106 AM. J. INT’L L. 1 (2012); Lassa Oppenheim, The Science of International Law: Its Task and Method, 2 AM. J. INT’L L. 313, 315 (1908) (“The rules of the present international law are to a great extent not written rules, but based on custom.”). 2 See Asylum case, supra note 1 at 276 (“The Colombian Government must prove that the rule invoked by it is in accordance with a constant and uniform usage practised by the States in question . . . .”); id. at 276-77 (holding that state practices were 1 Electroniccopy copyavailable available at: at: https://ssrn.com/abstract=3091912 Electronic https://ssrn.com/abstract=3091912