The European Union, China, California, and a number of U.S. states in the Northeast are currently using emissions trading as part of their efforts to reduce greenhouse gas (GHG) emissions. However, the popularity of emissions trading as a policy tool co-exists with a well-established, and increasingly politically powerful, set of critiques of it in the United States. These critiques come from environmental justice advocates as well as some academics and other observers. This Comment ventures to propose an innovative application for trading—the development of a municipal trading program to help reduce GHG emissions from buildings, which account for the lion’s share of many cities’ GHG emissions—and lays out two forms of the proposed policy mechanism that cities could implement.