State legislatures and environmental agencies have taken the lead in combating climate change, in the absence of leadership by the federal government. The most widely publicized efforts have involved the imposition of emission controls and fuel economy standards on motor vehicles by states such as California. But the states have also targeted stationary sources of greenhouse gases. In particular, they have sought to minimize carbon dioxide emissions from coal-fired power plants. States have used different approaches to reducing greenhouse gas emissions from electric utilities, including the adoption of renewable portfolio standards and cap-and-trade emission control programs. Increasingly, states are also simply refusing to allow the construction and operation of coal-fired electric plants. This article analyzes the Kansas Department of Health and Environment's decision in 2007 to deny a permit for two large coal-fired units. It assesses the merits of the utility's claims, advanced in ongoing litigation, that the state agency lacked the statutory authority to deny a permit based on the proposed units' impact on climate change. More broadly, it addresses the utility of statutory substantial endangerment provisions, modeled on provisions in the federal pollution control statutes, in restricting greenhouse gas emissions from stationary sources such as electric power plants. The article concludes that substantial endangerment provisions provide a useful mechanism for blocking the construction and operation of stationary sources that may contribute to climate change.