Workshop Customary International Law and its Interpretation in International Tax & Investment Law

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).

Customary international law (CIL), in turn, is one of the formal sources of international law 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 inductively through examination of two elements, state practice and opinio juris (acceptance as law).

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, despite the fact that it has been and remains the object of multiple studies and of application by almost all courts and tribunals. Evidently in the study of CIL there is a lacuna in understanding how CIL once it has been formed, continues to exist and is interpreted, and what is the nature and content of those interpretative rules.

In light of these developments and evolving views, this workshop aims to initiate a debate on the challenges and opportunities presented by CIL and its interpretation in two main fields, ie international tax law, and international investment law.

This conference is a cooperation of two European Research Council (ERC) Projects: TRICI-LAW researching on “The Rules of Interpretation of Customary International Law” and GLOBTAXGOV researching on “A New Model of Global Governance in International Tax Law Making”.