The present volume is the product of several years of research at the Institute for International Law of the Catholic University of Leuven, culminating in the defence of a doctoral thesis in October 2009. It has been made possible through the valued financial support of the Fund for Scientific Research Flanders (Fonds voor Wetenschappelijk Onderzoek Vlaanderen) as well as the even more valued moral support of my ever-energetic supervisor, Professor Jan Wouters. I thank my colleagues at the Institute for International Law and the Leuven Centre for Global Governance Studies for a very fruitful and most gratifying cooperation, in particular the former occupants of the ‘International House’ Dominic, Bruno, and Maarten, as well as Bart, Sten, Cedric, Fred and Viviane. I also wish to specifically thank several persons, who, in various ways, supported or inspired me during the task ahead, notably Ambassador Johan Verbeke and his former team at the Belgian Permanent Representation at the United Nations inNew York, ProfessorMichael Reisman of Yale Law School, Professors Christine Gray (Cambridge), Olivier Corten (Universite´ Libre de Bruxelles) and Dino Kritsiotis (University of Nottingham), as well as the Leuven faculty members who, with Professor Wouters, granted me the honour of serving onmy doctoral jury, Stephan Parmentier and Luc Reychler. My warmest thanks to my parents for their unremitting support and for instilling in me sufficient perseverance to cope with prolonged sojourns in the dusty catacombs of the Leuven university library.