The Clean Power Plan has been widely touted as significant because it regulates the largest source of carbon dioxide (CO₂) emissions in the United States – the electric power industry. Its significance, however, goes beyond U.S. CO₂ emissions because it serves as the linchpin of international efforts to reduce greenhouse gases in order to avoid dangerous climate disruption. The rule gave the Obama administration sufficient credibility to persuade the Chinese to pledge limits on their own greenhouse gas emissions for the first time and paved the way for worldwide pledges of significant emission reductions at the Paris Conference last December. If the U.S. fails to promptly implement this rule because of an unfavorable judicial ruling, the Paris agreement could unravel, as developing countries do not consider it equitable to demand reductions from them without significant reductions by the United States and other wealthy countries. 

Given the seriousness of global climate disruption and the Clean Power Plan's international role, the rule's survival matters more to achieving the Clean Air Act's stated goal – protecting public health and the environment – than any pollution reduction standard that the U.S. Court of Appeals for the D.C. Circuit …