WASHINGTON, DC — The U.S. Supreme Court Monday declined to consider a Bush-era rule that would have allowed a cap-and-trade approach to mercury, a toxic heavy metal emitted by power plants that burn coal and oil. Power plants are the largest source of mercury in the nation. The Supreme Court’s decision not to hear the case invalidates the U.S. EPA’s so-called Clean Air Mercury Rule, which would have allowed dangerous levels of mercury pollution to persist under a weak cap-and-trade program that would not have taken full effect until after 2020. The Supreme Court in effect denied an appeal, filed last year by a coalition of utilities, seeking reversal of a federal court decision vacating the mercury rule. The original lawsuit that resulted in the February 2008 U.S. Court of Appeals ruling in favor of the states and environmental groups maintained that EPA illegally removed coal and oil-fired power plants from the list of regulated source categories under a section of the Clean Air Act that requires strict regulation of hazardous air pollutants, including mercury. Left standing is the ruling by the appeals court that upheld the lower court ruling and rebuked the Bush-era EPA […]