As the United States and other developed countries have enacted or are in the process of developing legislation to cap greenhouse gas emissions post-2012, their policymakers are under increasing pressure from domestic constituencies to include trade measures as part of climate policy. This working paper analyzes relevant measures in emerging U.S. domestic climate policies, describes the objectives of these measures, assesses how they might be imposed, and discusses their implications for both a future climate agreement and the international trading system. It also touches on proposals to use trade measures in the European Union and other developed countries.