This book is necessarily devoted largely to the Vienna Convention on the Law of Treaties 1969. That law is the body of rules which determines whether an instrument is a treaty, how it is made, brought into force, amended, terminated and operates generally. It is not so concerned with the substance of a treaty (the rights and obligations created by it), which is known as ‘treaty law’. That is a matter for the negotiating states. For good reason, the Convention has been called ‘the treaty on treaties’. Although it does not occupy the whole ground, it covers the most important areas, and is the starting point for any description of the modern law and practice of treaties. It thus merits its own chapter. The other purpose of this chapter is to define the scope of this book by mentioning briefly those aspects of the law of treaties which the Convention does not deal with, but which will be covered here.

The UN General Assembly established the International Law Commission in 1947 with the object of promoting the progressive development of international law and its codification. The law of treaties was one of the topics selected by the Commission at its first session in 1949 as being suitable for codification. A series of eminent British international legal scholars (James Brierly, Hersch Lauterpacht, Gerald Fitzmaurice and Humphrey Waldock) were appointed as (successive) Special Rapporteurs.