On August 3, 2015, the U.S. Environmental Protection Agency (EPA) finalized the first-ever performance standards for carbon emissions from existing power plants in the United States under section 111(d) of the Clean Air Act. ____ Fed. Reg. ____. President Obama called the so-called “Clean Power Plan” “the single most important step America has ever taken in the fight against global climate change.” Whereas the proposed rule aimed to reduce carbon emissions from existing power plants by 30 percent compared to 2005 levels, the final rule is more ambitious, setting the goal at 32 percent. Under section 111 of the Act, performance standards for pollutants such as CO2 must be based upon the degree of emission limitation achievable through the application of the “best system…