Announcement: The Rules of Interpretation of Customary International Law Conference

The Rules of Interpretation of Customary International Law Conference. The TRICI-Law project, AthensPIL, the University of Groningen, and the Faculty of Law of the National and Kapodistrian University of Athens are hosting a conference on ‘The Rules of Interpretation of Customary International Law’. The conference will take place at the Faculty of Law of the University of Athens, on 12-13 October 2023. The aim of the conference will be to reflect upon the prospects, methods and limits of rules of interpretation of customary international law, focusing on both theoretical considerations and the practice of international (and domestic) courts in interpreting customary law across different fields of international law. Interested participants can join both online and in person. Registration is available here

Theme of the Conference

In international law, interpretation is ubiquitous and is the process through which the interpreter attempts to determine the true meaning of the rule that is being interpreted. Most cases brought before international courts and tribunals deal one way or another with questions of interpretation. This process has been codified in Articles 31-33 of the Vienna Convention on the Law of Treaties (VCLT). Based on these articles, some of the elements that are taken into consideration are the text, and context of the treaty, its object and purpose and the intention of the parties. However, a key issue is that these VCLT articles refer only to interpretation of treaties and not of customary international law.

Customary international law (CIL), in turn, is one of the formal sources of international law and together with treaties are the most important ones, creating binding rules of international law. Some of the most crucial rules of international law started and continue to exist as CIL. The issue with CIL, however, is that it is an unwritten source of international law. Its existence is determined through an examination of two elements, state practice and opinio juris.

Whereas in the application of treaties the process of interpretation is one that always yields a solution, with respect to CIL these rules of interpretation have not been examined. This leads to one of the following two paradoxical scenarios. Either CIL needs to be induced each and every time, by reference to state practice and opinio juris (but this is extremely problematic as it fails to take into account the continued existence, development and manifestation of CIL rules); or, CIL is asserted by international judges (which also runs into problems of a potential exercise of a  pouvoir de légiférer). Evidently, in the study of CIL there is a critical gap in understanding how CIL can be applied in individual cases once it has been formed. Even in the case of this unwritten source, i.e. customary international law (CIL), there are rules of interpretation that bear some similarity to those that exist for the interpretation of treaties.

Against this background, the Conference aims to reflect upon the prospects, methods and limits of rules of interpretation of customary international law focusing on both theoretical considerations and the practice of international (and domestic) courts and tribunals in interpreting customary law across different fields of international law. The overarching theme of the Conference is to discuss the patterns, methods and limits of interpretation of customary international law and the potential divergences of it from treaty interpretation To this end, the Conference aims to compile generalist contributions about the rules of interpretation of customary international law in the context of the theory of sources of international law, but also expert contributions about the rules, methods, and evolution of interpretation of customary law within specific sub-fields of international law.

During the Conference the Draft Conclusions of the TRICI-Law project and their commentaries will also be discussed.