Research Handbooks in International Law series
Edited by Christian J. Tams, Antonios Tzanakopoulos and Andreas Zimmermann
Chapter 1: The law of treaties; or, should this book exist?
This short chapter is not about rules of international law applicable to treaties. It is about the concept of ‘the law of treaties’ as a subject or topic within international law. It takes as its starting point the conception of treaties, which is the paradigm implicit in the 1969 Vienna Convention on the Law of Treaties. That paradigm is of a written instrument negotiated by the States parties to it, where the binding force comes from the consensus ad idem. It is a clearly consensualist model, as befits a body of doctrine whose roots lie in consensualist conceptions of international law in general. The main argument of the chapter is that ‘the law of treaties’ may no longer be the most useful way of approaching legal obligations voluntarily assumed by States. The law of treaties is a curious phenomenon. It has the appearance of solidity and certainty. Scarcely any piece of international litigation does not include in its overture a reference to the rules on treaty interpretation that are contained in the Vienna Convention. That almost ritualistic reference commonly continues with an assertion that the Vienna Convention is regarded as an accurate statement of customary international law; and in most cases that assertion is accepted without demur. And in many cases the court or tribunal is spared a reading of the relevant provisions of the Vienna Convention on the ground that they are too well known to need repetition.