This book combines an insight into the legal aspects of operations conducted as part of the European Security and Defence Policy (ESDP) of the EU along with an analysis of the status and obligations of international organizations under international law. It then applies the findings to the law of armed conflict and human rights in relation to ESDP operations. Part I describes and analyzes the ESDP, including all 22 military and civilian crisis management operations launched up to August 31, 2009, as well as developments under the Lisbon Treaty, and briefly discusses the international law issues raised, offering a unique insight into ESDP practice and its legal aspects. Part II examines this practice in the framework of the status and obligations of international organizations under international law. It looks at the legal status and personality of international organizations and of the EU, as well as how international organizations, including the EU, are bound by international obligations. Part III extensively addresses the international law applicable to the conduct of ESDP operations, in particular the law of armed conflict and international human rights law, filling a gap in the literature. Frederik Naert received a special mention from the Jury of the 2012 Ciardi Prize for his book International Law Aspects of the EU's Security and Defence Policy, with a Particular Focus on the Law of Armed Conflict. The Ciardi Prize is awarded annually to a substantial and original study dealing with military law, law of war or any matter connected with or related to the aforementioned.