The three volumes of Customary International Humanitarian Law by Jean-Marie Henckaerts and Louise Doswald-Beck (the Study) constitute a monumental work which has given rise to a huge amount of interest and discussion throughout the world. As is said in chapter§1 of the present book, all those associated with the preparation of the Study are to be congratulated: in focusing on the actual practice of States they have brought us closer to the heart of international humanitarian law. It is the unanimous view of the authors of this book that the Study represents a valuable work of great service to international humanitarian law. This book is intended as a complement to the Study – and as a compliment to it.

The book emerged from meetings of a group assembled to discuss the Study at the British Institute of International and Comparative Law during 2005/2006. Following a conference at Chatham House to launch the Study in the United Kingdom in April 2005, it was decided that further discussion and analysis would be valuable and would also be in keeping with the spirit expressed by Yves Sandoz in his Foreword to the Study: