2022 Statelessness & Citizenship Review 4(1) on the international agenda, through hosting events and pressuring states to resolve statelessness. UNHCR has urged states to adopt birth registration and statelessness determination procedures, revise domestic law and adhere to the 1961 Convention on the Reduction of Statelessness (‘1961 Convention’), among other initiatives.2 Due to this campaign, states are increasingly reforming their practices to provide for nationality from birth for stateless children as well as increasingly revising their opinions and expressing that such solutions are desirable, necessary and morally compelling. Today, thanks in large part to UNHCR’s efforts, the international community can now confidently conclude that state practice and opinio juris support a norm that states have an obligation to grant nationality to children born in their territories when the child would otherwise be stateless. The question of customary international law in such a situation would bring helpful certainty to hundreds of thousands of children. It is true that treaty law can arguably already be interpreted to provide for a rule requiring nationality in such cases. The 1961 Convention requires states to grant nationality to stateless children born in their territory and the right to a nationality in the International Covenant on Civil and Political Rights (‘ICCPR’) could be interpreted to also require it, especially in light of the requirement in the Convention on the Rights of the Child (‘CRC’) that states apply the law in the best interests of the child. However, the 1961 Convention still does not have universal adherence and this interpretation of the ICCPR and CRC has not yet been authoritatively confirmed. With these gaps, it is more challenging to identify the state obliged to grant nationality and, in turn, secure birth registration and the rights that follow, such as education rights. Customary international law, if it can be shown to exist, could fill these gaps and provide a single, predictable and consistent rule that covers cases of statelessness at birth, applicable to all states in the world. This article will update the prior research with the most recent, and quickly changing, practice and expressions of opinio juris, partly as influenced and documented by UNHCR as a part of the #IBelong Campaign. In doing so, it will explore a case study that demonstrates that the influence of an international organisation can push states to revise their practice and develop new views on the law. It will conclude by confirming that this norm surely exists under customary international law. METHODOLOGY OF CUSTOMARY INTERNATIONAL LAW As is well known, customary international law arises when there is sufficient state practice and opinio juris.3 This source of law was identified in the Statute of the 2 3 For example, in July 2020, UNHCR hosted a High-Level Segment where many states pledged to reform their approach to statelessness: see UNHCR, High-Level Segment on Statelessness: Results and Highlights (Report, May 2020) 20–43 <https://www.refworld. org/docid/5ec3e91b4.html> (‘High-Level Segment Results and Highlights’); UNHCR, The Campaign to End Statelessness: April–June 2020 Update (Report, 16 July 2020) (‘#IBelong Campaign Update June 2020’). See SS ‘Lotus’ (France v Turkey) (Judgment) [1927] PCIJ (ser A) No 10, 18 (‘Lotus’); Asylum Case (Colombia v Peru) (Judgment) [1950] ICJ Rep 266, 276–77; North Sea Continental Shelf Cases (Germany v Denmark; Germany v Netherlands) (Judgment) [1969] ICJ Rep 3, 44 (‘Asylum Case’); Report of the International Law Commission, Sixty-Eighth Session, 2016: Draft Conclusions on the Identification of Customary International Law Adopted by the Commission, UN Doc A/71/10 (2 May–10 June and 4 July–12 August 2016) 76 [62] conclusions 2, 3(2) (‘ILC Draft Conclusions’). 114