This focused collection of essays on various aspects of the law of treaties does justice to its honoree, scholar and author Professor Bert E.W. Vierdag, on the occasion of his retirement as Professor of International Law and International Relations at the University of Amsterdam. Written by leading academics in the field as well as practitioners and former practitioners, the essays cover: - the alignment of treaties with more general sources doctrine, addressing such issues as conflicts between various types of treaties and the relationship between treaties and customary international law, and between treaties and domestic law; - the emergence of treaty norms through various ways and methods; and - the creation of treaty law in several branches of international law. This cohesive, focused, expert work will assist and appeal to both academics in the fields of public law and political science and professionals engaged in international negotiations and treaty-making.