Treaty Interpretation and Constitutional Transformation: Informal Change in International Organizations

Abstract

This Article presents an argument about the constitutional transformation of international organizations through the judicial interpretation of their constituent instruments. The organizations at issue are public institutions, established by international agreement and charged with the exercise of transnational governmental power. They are, on one view, essentially treaty-based organizations that derive authority from the consent of the Parties. At the same time, these organizations must be understood as constitutional bodies, constituted with substantial delegated powers and varying degrees of independence vis-a-vis their constituent Member States. Some have developed the capacity to evolve over time, informally and autonomously. I argue that the judicial organs of certain organizations have transformed their material constitutions by engaging in particularly liberal approaches to the interpretation of their constituent instruments. The analysis focuses on one particular technique of interpretation: the doctrine of interpretation on basis of the subsequent practice of the States Parties. I trace the use of this doctrine by three judicial bodies: the World Trade Organization Appellate Body, the International Court of Justice (ICI), and the European Court of Human Rights (ECtHR). The first organ represents a control, implementing a strict approach to subsequent practice. By contrast, I suggest that the ICJ and ECtHR have each adopted radically expansive approaches to subsequent practice, with the effect of transforming the powers and autonomy of the organizations to which they belong.