The Laeken Council Declaration of 2001 committed the European Community to a constitutional reform that aimed at enhancing the legitimacy of EU governance through “more democracy, transparency, and efficiency”. In the area of Common Commercial Policy (CCP), the coming into force of the Treaty of Lisbon on December 1, 2009, responded to the Laeken Declaration with the most extensive reform in history and substantially amended applicable provisions on decisionmaking, scope of EU exclusive competence, objectives, and principles. Against the benchmark set out by the Laeken Council objectives, this study examines the law, practice, and quality of institutional change in CCP governance after Lisbon. To this end, the study advances a twofold comparative institutional analysis that is based on a transaction-cost approach to the understanding of legal, political, and informal institutions that govern the CCP and EU external economic relations more broadly. The study finds that the reallocation of horizontal competences among EU institutions through the empowerment of the European Parliament has generally decreased the process efficiency of the CCP. At the same time, it has markedly decreased the cost of political participation for public and private stakeholders and introduced increasingly effective democratic control to the now bicameral system that governs the CCP in the Lisbon era. Parliamentary involvement, moreover, has radically enhanced process and substantive transparency and opened a space for public deliberation of external economic policy. Opinion 2/15 of the Court of Justice of the European Union has, secondly, confirmed the Treaty-induced tectonic shifts in the allocation of vertical competences. It is argued that the Court’s Opinion sets incentives for a fundamental change of the institutional practice that governs the conclusion of EU external economic agreements. Ending the tradition of ‘mixed’ agreements in favor of ‘EUonly’ treaty conclusion would further approximate the achievement of all three Laeken Council objectives and render EU external economic governance more efficient, effective, representative, and legitimate. In order to fully employ the democratic potential of ‘EU-only’ CCP governance, however, such practice will require the reinforcement of national parliamentary engagement in that process.