Effectiveness and Evolution in Treaty Interpretation
Authors: Rietiker Daniel 
Published: September 2019

Effectiveness and evolution in treaty interpretation have to be placed in the context of treaty interpretation more generally, which is one of the classical topics of public international law. For some authors, there is a link between these two elements, insofar as the principle of dynamic (or evolutive) interpretation aims to ensure the effective application and implementation of treaties. Therefore, it is appropriate to analyze them together. The majority of authors, however, concentrate on one aspect. Regarding, first of all, effectiveness, such a principle has not been explicitly enshrined in the 1969 Vienna Convention on the Law of Treaties (VCLT), but it can nevertheless be considered an underlying principle of that instrument. In particular, the flexibility of the concept of the object and purpose of a treaty allows for the consideration of effectiveness. Other tools for effectiveness are teleological interpretation and interpretation according to the effet utile (ut res magis valeat quam pereat), but neither authors nor practice systematically distinguish between those concepts and principles. In addition, judicial and quasi-judicial bodies implementing certain treaties, in particular human rights instruments and constitutive agreements of international organizations, have adopted their own principles of effectiveness, such as the principle that calls for a “practical and effective” protection of human rights or, regarding international organizations, the doctrine of implied powers. Second, the notion of evolution in interpretation raises issues of intertemporal law, namely the question as to which moment is relevant for the interpretation, i.e., the moment of the conclusion of a treaty or the moment when a dispute necessitating interpretation arises. The analyzed literature shows that, generally speaking, practice and theory seem to favor a dynamic and evolutive interpretation within appropriate and reasonable limits, justifying such an approach, inter alia, by the special nature of certain treaties. As far as the relevant practice of international courts is concerned, human rights tribunals, in particular the European and the Inter-American Court of Human Rights (ECtHR and IACtHR), both adopting a dynamic and effective interpretation, have received significant doctrinal attention in this regard. For the authors, the special nature and purposes of those treaties justify a flexible, evolutive, and effective approach. The same can be said for the Court of Justice of the European Union, having relied heavily on interpretation according to the effet utile of a treaty. The practice of the Permanent Court of International Justice (PCIJ) and the International Court of Justice (ICJ), both dealing with inter-State complaints, are not surprisingly less nuanced concerning effectiveness and evolution, but have nevertheless shown a clear trend in that direction more recently. Finally, the analysis of the practice of the World Trade Organization (WTO) Appellate Body, which deals with inter-State claims too, is more ambiguous, but it is generally suggested that its interpretation is less guided by considerations of effectiveness and evolution than, inter alia, the practice in the field of human rights.