Beyond Self-Defence:

Reassessing the Law on the Use of Force after the US–Iran War under the UN Charter and Islamic International Law

Faizah Rahim

Nehaluddin Ahmad

 

Abstract: The 2026 US–Iran War has renewed important debates on the contemporary law governing the use of force. Although much existing discussion has centred on Article 51 of the Charter of the United Nations, this article argues that the conflict raises wider concerns about the resilience of the post-1945 jus ad bellum (right to war) framework. It contends that expansive self-defence claims, preventive security reasoning and unilateral uses of force risk weakening the prohibition on force under Article 2(4) of the UN Charter. Against this background, the article reassesses the law on the use of force through a comparative analysis of the UN Charter and Islamic International Law, or al-Siyar. It examines the UN Charter framework alongside Islamic principles of necessity, proportionality, justice, restraint, treaty obligation, civilian protection and peaceful settlement. Using the US–Iran War as a contemporary case study, the article finds that recent State practice reflects pressure upon the existing jus ad bellum framework rather than a legitimate basis for expanding self-defence. It further argues that both traditions treat armed force as an exceptional measure restrained by law, justice, good faith and the pursuit of peace.