The U.S. Supreme Court rejected a bid to delay the U.S. Environmental Protection Agency's controversial mercury air toxics rule. A day earlier, the EPA argued that the D.C. Circuit reasonably exercised its discretion not to vacate the regulations during the agency’s revision process.

Chief Justice John Roberts gave no written explanation for his denial of last week's request by 20 states to stay the EPA’s Mercury and Air Toxics Standards rule, which requires coal-fired power plants to slash mercury and other toxic emissions. The states argued that without a stay, the Supreme Court’s June decision in Michigan v. EPA would be thwarted.

The states argued that although that ruling held that the Clean Air Act requires the EPA to consider costs before it may impose any rule, the D.C. Circuit wrongly left the original rule in place while the agency revamped it.

The industry intervenors are represented by Brendan K. Collins, Robert B. McKinstry Jr., Ronald M. Varnum and Lorene L. Boudreau of Ballard Spahr LLP.