Dramatic events in Kosovo and East Timor have raised fundamental questions about international law on the use of force: was NATO entitled to exercise a right of humanitarian intervention to protect the ethnic Albanians of Kosovo by its bombing campaign? What power did the United Nations have to send a UN force, or to authorize an Australian-led force, to stop the fighting that escalated when the people of East Timor voted for independence? This book aims to cover the whole of the large and controversial subject of the use of force in international law; it examines not only the use of force by states but also the role of the UN and regional organizations in the maintenance of international peace and security. The focus is on state practice in the light of doctrinal debates. During the Cold War and the decolonization process states and writers were divided as to the scope of the right of states to use force in self-defence, to further self-determination and to intervene in civil wars. It is now time to reappraise these differences and to assess how far the end of the Cold War has brought greater agreement This book is intended for academics and students working in international law