The institutional foundations of intergovernmentalism and supranationalism in the European Union

We present a unified model of the politics of the European Union (EU). We focus on the effects of the EU's changing treaty base (from the Rome to Amsterdam Treaties) on the relations among its three supranational institutions-the Commission of the European Communities, the European Court of Justice, and the European Parliament-and between these actors and the intergovernmental Council of Ministers. We analyze these institutional interactions in terms of the interrelationships among the three core functions of the modern state: to legislate and formulate policy (legislative branch), to administer and implement policy (executive branch), and to interpret policy and adjudicate disputes (judicial branch). Our analysis demonstrates that the evolution of the EU's political system has not always been linear. For example, we explain why the Court's influence was greatest before the passage of the Single European Act and declined in the following decade, and why we expect it to increase again in the aftermath of the Amsterdam Treaty. We also explain why the Commission became a powerful legislative agenda setter after the Single European Act and why its power today stems more from administrative discretion than from influence over legislation.