The fifth edition of this book that appeared in 2003 has been extensively revised. To mark the growing importance of the international prosecution of alleged war criminals and others accused of egregious crimes, a new chapter on Individual Criminal Responsibility in International Law has been introduced. The chapter on Air and Space Law has had to be removed, with the section on Outer Space being moved to the chapter on Territory. The increasing significance of the International Court of Justice is recognised by devoting a separate chapter to it. The section on the International Tribunal for the Law of the Sea has been moved to the chapter on the Law of the Sea. The other chapters in the book have been re-examined, updated and, where necessary, rewritten. I have also been able to correct some errors. I am particularly delighted that the book has been translated into, among other languages, Chinese, Polish, Hungarian and Portuguese and I am very grateful for the work of all those involved. I would especially like to thank Sinead Moloney of Cambridge University Press for her encouragement, assistance and above all patience. Particular gratitude is owed to Merel Alstein for her meticulous research assistance and for updating the web reference section. I am, once again, very grateful to Diane Ilott for her careful and thorough copy-editing and to Maureen MacGlashan for so carefully preparing the index and tables respectively. A debt remains to Sir Elihu Lauterpacht QC for his encouragement in the early development of this work. I also remain grateful to my many colleagues from many countries for their advice and encouragement, while reassuring them that all responsibility for the end product rests squarely with me.