The events relating to Iraq have been critical in defining the post-Cold War inter- national system of peace and secnrity. Dealing with Iraq covered the whole legal, political and emotional spectrum. The initial triumphalism was replaced by cyni- cism and apathy, ending in division and enmity. Above all, it raised questions about the political and legal foundations of the international secnrity system, its players and their interests. The object of the present paper is to examine the cnr- rent meaning and nature of the collective secnrity system premised on the United Nations. An understanding of the flaws and problems associated with the prac- tice of this system will enable us to rethink its basis and propose a conceptual framework for its reconstitution on the basis of legitimacy, using the war on Iraq as a case study to illustrate onr arguments. The discussion will begin with a short presentation of the political and legal situation leading to the war against Iraq in March 2003. This will be followed by a critical analysis of the UN collective se- cnrity architecture as it evolved after the end of the Cold War. Onr aim at this stage is to identify the characteristics of the system, consider the scope of subse- quent developments in conceptual or practical terms and discuss their signifi- cance for the international secnrity system.