About the Book:This highly original and challenging study offers an examination of the tensions which exist between the two most important sources of international law: Treaty and Custom. Through detailed analysis of state practice and key decisions of international tribunals, the author considers the circumstances by which new customary law may abrogate the obligations of a prior treaty, and argues that there is a special category of situations which supports the right of a state to renegotiate a treaty by an appeal to new customary law. Scholarly and thought-provoking, this is an original and, at times, controversial study which will become essential reading for all those interested in the sources of international law and the observance and enforcement of treaty obligations.