Now in its fourth year, the Max Planck Yearbook of United Nations Law is becoming a much sought-after forum for essays by the most distinguished professors in international law. These essays cover a variety of topics related to the activities of the United Nations: from the role of the Security Council to UN treaties, from environmental issues to humanitarian law. Volume 4 focuses on new trends in the enforcement of erga omnes obligations and the role of International Law after Kosovo. It also contains topical articles such as "The International Labour Organization in its Second...