In line with accepted theories of environmental law, many prominent environmental law scholars have dismissed the climate change plans of U.S. cities and other local governments, presuming that these efforts will have no more than a trivial effect on greenhouse gas emissions. Drawing upon economic theories, others find local “piecemeal” efforts not only ineffective, but also potentially harmful to the prospects for a successful national emissions reduction program. In contrast, this Article argues that local governments have core regulatory powers in domains that will prove critical to a comprehensive response to climate change. Following a trend in scholarship that moves away from rigid prescriptions for either centralized or decentralized environmental regulation, this Article envisions local governments as important players in a multilevel governmental effort that regulates greenhouse gas emissions from the bottom up and the top down.