The decision of the European Community (EC) members to complete their internal market is an important instance of international cooperation. The economic objective is to remove a wide array of nontariff barriers to trade that elsewhere have proved intractable. The institutional structures established to reach this goal heavily constrain the autonomy of sovereign states and cannot be explained by traditional theories of international cooperation that focus on the efficiency of solutions to collective action problems. Many forms of trade liberalization would have represented Pareto improvements for the EC. The specific choices made, such as the reform of decision making by the Council of Ministers, the EC Commission, and the European Parliament, reflected the relative bargaining power of the various member states. This bargaining power was influenced by asymmetries in economic dependence, differences in time horizons, and differences in domestic constraints on national governments. Specifically, the choices reflected the preferences of France and especially Germany, which can be expected to benefit considerably from the economic outcomes generated by the institutional structures of the internal market.