The Obama EPA has put forth several actions to regulate the emissions of greenhouse gases from stationary sources. These regulatory developments take place in the context of failed efforts to pass comprehensive federal legislation and the Supreme Court’s death blow to federal common-law remedies. Two of the Administration’s regulatory initiatives—the Endangerment Finding and the embrace of greenouse gases in the prevention of significant deterioration program—are embroiled in litigation, the outcome of which may not be known for some time. The Administration’s new source performance standard for electric generating units has yet to be proposed. Actual reductions in greenhouse gas emissions achieved through these rules will not be knowable for years.