Treaty Interpretation under the Vienna Convention on the Law of Treaties

Published: 23 June 2026
The core purpose of the International Fiscal Association (IFA) is the study and advancement of international tax law. Since its creation in 1938, IFA has quite naturally extensively focused on tax treaty law, which to date continues to represent the primary source of international tax law. Over the years, distinguished members of IFA have repeatedly considered the interpretation of tax treaties in light of the rules of the Vienna Convention on the Law of Treaties (VCLT). The role and status of the OECD commentaries in tax treaty practice has equally been explored on numerous occasions both at IFA Congresses and during branch meetings. In recent years, however, tax treaty interpretation has faced new challenges. On the one hand, the emergence of new international standards and rules has prompted novel interpretative questions. On the other hand, court decisions dealing with tax treaty interpretation continue to be on the rise. Finally, as the principles of tax treaty interpretation evolve, their relationship with those of general international law requires increased attention. Against this background, this book revisits tax treaty interpretation in light of the rules of the VCLT with a threefold objective. First, the book assesses the consistency of tax treaty interpretation with the general framework provided by the VCLT and, more broadly, that of public international law. Second, this volume identifies the specificities of tax treaty interpretation (notably its relationship with domestic law) and the challenges that such specificities present. Third, the book deconstructs the most relevant tax treaty interpretation questions occurring in practice as well as the current trends in judicial decisions on tax treaty interpretation. The book comprises two general reports prepared by its editors which build on the topical chapters written by leading experts on tax treaty interpretation. It serves as a reference guide to practitioners (particularly those involved in tax treaty controversies), treaty negotiators, representatives of international organizations, policymakers and scholars.
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