Forthcoming in the Max Planck Yearbook of United Nations Law (27) I. Introduction The International Law Commission (ILC) has helped reduce the uncertainty and indeterminacy that characterizes a decentralized, international legal system. In line with its mandate to promote the progressive development of international law and its codification, the Commission has produced a vast number of draft articles, guidelines, conclusions, and studies on various topics. For one, the ILC is usually lauded for successfully codifying key areas of international law, such as the law of treaties, the law of diplomatic and consular relations, the law on the high seas, and the law of responsibility. Yet, its contribution to the development of the law on areas that are not intuitively within its purview is only rarely accounted for.2 The international law on migration seems to be a case in point. Although migration as such was only briefly considered as a topic by the ILC,3 the protection of migrants, refugees, and stateless persons has come to figure prominently in various of its codification projects: from nationality and statelessness, state succession, expulsion of aliens, and diplomatic protection to crimes against humanity and the ongoing debates on sea-level rise in relation to international law. Still, there seems to be relatively scarce research being conducted on the development of international migration law by the International Law Commission. See for instance, R. O’Keefe, ‘The ILC’s Contribution to International Criminal Law’ (2006) 49 German Yearbook of International Law 201-257; J. Harrison, ‘The International Law Commission and the Development of International Investment Law’ (2013) 45 George Washington International Law Review 1-30; A. Boyle, ‘Codification of International Environmental Law and the International Law Commission: Injurious Consequences Revisited’ in A. Boyle and D. Freestone (eds), International Law and Sustainable Development: Past Achievements and Future Challenges (Oxford University Press 1999) 61-85; N. Oral, ‘The International Law Commission and the Progressive Development and Codification of Principles of International Environmental Law’ (2019) 13 FIU Law Review 1075-1100. 3 Apart from being suggested as a topic for the Commission’s long-term programme of work in the 1990s. See UN ILC, ‘Report of the Commission to the General Assembly on the Work of its Forty-Third Session’ in Yearbook of the International Law Commission 1991, vol. II (Part Two) UN Doc. A/CN.4/SER.A/1991/Add.l, at 130. 2 2 Electronic copy available at: https://ssrn.com/abstract=4816199