The twelve-day conflict between Iran and Israel and the direct entry of the United States into this conflict once again challenged the foundations of the international legal order, especially the principle of prohibition of the use of force. The present note, which aims to provide a comprehensive and analytical framework based on the speeches of experts in law and international relations at the specialized meeting of the Iranian Association for United Nations Studies on the “Twelve-Day War between Israel and Iran” held on 17 Tir 1404 at the House of Humanities Scholars, examines various aspects of this conflict from the perspective of international law. The first part provides a historical look at the relations between Iran and the International Atomic Energy Agency and its role in the context of the recent conflict. The second part is dedicated to the nature of the “threat of force” in international law, the criteria for its validity, the difficulty of attributing political slogans to states, and the doctrine of “state survival” in the context of mutual claims between Iran and Israel. The third section analyzes the US innovation in conceptualizing and applying “preemptive and preemptive self-defense” and its efforts to transform it into customary practice. The fourth section addresses the fundamental challenges of international humanitarian law in this confrontation, including the recognition of the beginning of an armed conflict, attacks on nuclear facilities, and the targeting of civilian scientists. Finally, the fifth section examines the concept of espionage in peacetime and wartime, the legal status of spies, and a critique of Iran’s hasty domestic legislation in this area. This article emphasizes that despite the frustration caused by repeated violations of fundamental rules, the defense of international law remains a necessary and powerful tool for countries like Iran. The session opened with a welcoming opening speech by Dr. Mosaffa, President of the Iranian Association for United Nations Studies, and concluded with a question and answer session between the audience and the speakers.