Annexation: a threat that never fades

Abstract This article examines the doctrinal stability and practical fragility of the international legal prohibition of annexation and evaluates how the UN Charter system has operated against annexation in practice. It clarifies the taxonomy of annexation—distinguishing de jure and de facto annexation from belligerent occupation—and traces the sources grounding the non-acquisition rule and the corresponding duties of non-recognition and non-assistance. Building on Brunk and Hakimi’s argument that the prohibition of annexation is an autonomous norm not reducible to Article 2(4), this article assesses how far the Charter-era jus ad bellum architecture has nevertheless treated ‘force’ as its organizing centre, and what this has meant for enforcement. It then evaluates effectiveness across selected cases using three criteria: deterrence ex ante, remedy ex post, and consistency across like cases. The study finds a mixed record: while doctrine is comparatively stable, inconsistent enforcement and selective (non-) recognition have limited deterrence, complicated reversals, and produced uneven treatment, with implications for self-determination and customary law. Rather than proposing to redefine Article 2(4), this article argues that today’s principal risks lie in post-force consolidation, pretextual justifications, and other strategies that shift contestation to the ‘force’ characterization while annexation’s autonomous consequences remain engaged. The conclusion urges more consistent application of non-recognition and non-assistance to prevent faits accomplis from hardening into tolerated title.