Formalism versus flexibility in the law of treaties

This contribution aims to show that the dominance of formalism in treaty law is much more nuanced and qualified than the general perception sketched out in the preceding paragraph suggests. It will be argued that from its making to its termination, a treaty see-saws between formalism and flexibility, and that the body of rules designed by international lawyers to regulate the life of treaties mirrors this constant oscillation: the law of treaties, as codified in the two Vienna Conventions, displays both formal rationality and flexibility. This chapter aims to shed some light on the various, and disparate, features of this fundamental tension.

It is more specifically submitted here that the oscillation between formal rationality and flexibility comes to a head at three different levels: at the moment of the creation of the treaty, at the moment of its validation and identification as a treaty properly so-called and, finally, at the moment of its application, that is when the provisions of a treaty are confronted with the facts and accordingly need to be interpreted. At each of these stages, the tension between formal structures and flexibility is solved according to a different equilibrium. The different balances struck are themselves unstable and in a constant state of flux, for they are treaty-dependent and have not been definitively concretized by the rules of the Vienna Conventions. It is true that the constant oscillation between formalism and flexibility also infuses the rules on suspension and termination. However, as suspension and termination form the subject of a separate contribution, the ‘un-making’ of treaties will be addressed only briefly.