The EU Emissions trading scheme has been characterized as one of the most far-reaching and radical environmental policies for many years. Given the EU's earlier resistance to this market-based and US-flavored program, the development and implementation of the carbon emissions trading program has been rapid. This novel approach to environmental regulation has the potential to dramatically change international strategies for environmental protection. Understanding the origins and evolution within the EU is an important case study that offers significant contributions to the literatures on policy learning and diffusion as well as multilevel governance.