Although a great deal of research has been done on the process of constitutionalization of the European Union by its Court of Justice, there seems to be a missing link in the existing literature: the part played by jurists themselves in this legal revolution, particularly by judges and advocates-general of the Court. This article analyzes the social recruitment to the nascent Court of Justice (in the 1950s and '60s) in order to assess the impact of their career trajectories on their conception of the legal "nature" of the European Communities, particularly whether EC law should be regarded as "domestic", rather than "international" law, and therefore equivalent to a constitution.