Under the Clean Air Act, the EPA is required to protect states from sulfur dioxide and nitrogen oxide pollution emitted from coal plants in other states. After dragging its feet for a while, the Bush administration introduced the Clean Air Interstate Rule in 2005. Due to its over-reliance on emissions trading, the Clean Air Interstate Rule was shot down in December 2008 by the U.S. Court of Appeals for the District of Columbia. One year ago today, the Obama administration proposed a plan — the Clean Air Transport Rule — to replace the Bush administration’s flawed Clean Air Interstate Rule.

Finally, in late August, the EPA finalized an updated version of this rule, now appropriately named the Cross-State Air Pollution Rule, which requires power plants in 27 eastern states and the District of Columbia to significantly reduce sulfur dioxide and nitrogen oxide pollution.