Recent constitutional thinking has directed its attention to the profound impact of soft' norms on the way legislation is made. This book identifies the European Union's impact assessment regime as a source of these norms. In 2002 the European Commission - later followed by the European Parliament and the Council of Ministers - committed to performing rigorous assessment of the economic, social and environmental impacts of policy options before adopting (legislative) proposals. Applying a constitutional lens' to this regulatory' topic, Anne Meuwese examines both the details and the framework of IA in EU lawmaking to date, drawing attention to its strengths, its contradictions, and its power to enhance the deliberative quality of legislative debates.