Sea-level Rise and Continuity of Statehood

Sammanfattning

Sea-level rise caused by anthropogenic climate change poses an unprecedent-ed challenge to international law. For Small Island Developing States (SIDS), the prospect of partial or complete territorial inundation raises fundamental questions concerning the continued existence of States whose territory may become uninhabitable or disappear entirely. Under traditional interpretations of the Montevideo Convention on the Rights and Duties of States, territory constitutes a central element of statehood. At the same time, international law has long recognized a strong presumption in favor of state continuity, even where States experience profound changes to their territory, population, or governmental structures. This thesis examines whether, and on what legal basis, the continuity of state-hood for SIDS threatened by climate-induced territorial loss can be reconciled with the territorial requirement of international law. Employing a doctrinal legal methodology, the study analyses treaties, customary international law, judicial decisions, institutional materials, and legal scholarship. Particular at-tention is devoted to the doctrine of state continuity, the work of the Interna-tional Law Commission (ILC) Study Group on Sea-Level Rise in Relation to International Law, the 2025 Advisory Opinion of the International Court of Justice (ICJ) on Obligations of States in Respect of Climate Change, and re-cent State practice, including the Falepili Union Treaty, the Pacific Islands Forum (PIF) Declaration on the Continuity of Statehood, and the AOSIS Declaration on Sea-Level Rise and Statehood. The thesis finds that international law increasingly supports a presumption of state continuity notwithstanding climate-induced territorial loss. While the Montevideo criteria remain central to the creation of States, they do not rigidly govern state continuity. Contemporary institutional developments and emerg-ing State practice indicate that continuity may be preserved through an inter-pretation of territory that emphasizes its functional role in enabling govern-ance, jurisdiction, and political community rather than its purely physical ex-istence. Accordingly, the loss of habitable territory does not necessarily entail the extinction of statehood where a coherent political community, governmen-tal structures, and international recognition persist. The study further demonstrates that this reconciliation carries significant im-plications for the doctrine of statehood. Effectiveness is increasingly under-stood in institutional and relational rather than exclusively territorial terms, recognition assumes a more prominent role in sustaining continuity, and sov-ereignty may be exercised through cooperative and extraterritorial arrange-ments. The thesis concludes that the emerging presumption of continuity re-flects an adaptation of international law aimed at preserving legal stability, self-determination, and international legal personality in the face of climate-induced territorial loss.