The Right of Self-defence and Third State Provision of Arms: Reflections on the Current Debate

Abstract The article examines the legal implications of third-State military assistance in the context of Ukraine’s self-defence against Russian aggression, focusing on the intersections of jus ad bellum, jus in bello , and the law of neutrality. It evaluates whether military aid, such as weapon provision and intelligence sharing, constitutes an indirect use of force under Article 2(4) of the UN Charter or implicates assisting States as parties to the conflict. The article critiques expanding the notion of indirect force to State-to-State assistance and discusses the implications of collective self-defence and the law of neutrality in light of the UN Charter law and the peremptory norm of prohibition of the use of force, including aggression. The analysis concludes that lawful assistance to a State exercising self-defence does not breach international law, emphasizing the superiority of jus cogens norms over conflicting legal provisions, such as neutrality.