This new edition of a textbook first published in 2000 provides a comprehensive account of the law of treaties from the viewpoint of an experienced practitioner. As such, it is the first, and only, book of its kind. Aust provides a wealth of examples of the problems experienced with treaties on a daily basis, not just when they are the subject of a court case. He explores numerous precedents from treaties and other related documents, such as memorandums of understanding (MOUs), in detail. Using clear, accessible language, the author covers the full extent of treaty law, drawing examples from both treaties and MOUs. Modern Treaty Law and Practice is essential reading for teachers and students of law, political science, international relations and diplomacy, who have an interest in treaties.