The European Court of Justice has been the dark horse of European integration, quietly transforming the Treaty of Rome into a European Community (EC) constitution and steadily increasing the impact and scope of EC law. While legal scholars have tended to take the Court's power for granted, political scientists have overlooked it entirely. This article develops a first-stage theory of community law and politics that marries the insights of legal scholars with a theoretical framework developed by political scientists. Neofunctionalism, the theory that dominated regional integration studies in the 1960s, offers a set of independent variables that convincingly and parsimoniously explain the process of legal integration in the EC. Just as neofunctionalism predicts, the principal forces behind that process are supranational and subnational actors pursuing their own self-interests within a politically insulated sphere. Its distinctive features include a widening of the ambit of successive legal decisions according to a functional logic, a gradual shift in the expectations of both government institutions and private actors participating in the legal system, and the strategic subordination of immediate individual interests of member states to postulated collective interests over the long term. Law functions as a mask for politics, precisely the role neofunctionalists originally forecast for economics. Paradoxically, however, the success of legal institutions in performing that function rests on their self-conscious preservation of the autonomy of law.