On Thursday, February 3, 2016 the United States Supreme Court, in an order issued by Chief Justice John Roberts, refused to grant a stay of the Environmental Protection Agency’s (EPA) Mercury and Air Toxics Standards for coal-fired power plants (MATS). By denying the stay, Chief Justice Roberts allowed the Standards to remain in place while EPA reconsiders the costs associated with its implementation.

The Supreme Court ruled in June 2015 that EPA had improperly failed to consider those costs prior to deciding to regulate the harmful emissions, and remanded MATS to the DC Circuit for a determination of how EPA was to consider those costs. In December, the DC Circuit held that EPA could leave the rule in place while it reviewed compliance costs; EPA’s updated findings, anticipated in April, will also be subject to review at the DC Circuit.

The Court’s denial of the stay request may ultimately be of minimal effect, as many utilities were already taking steps to comply with MATS even before the Court’s June 2015 ruling. The denial does, however, indicate that the Court’s decision last month to grant a stay of EPA’s Clean Power Plan pending the outcome of litigation at the DC Circuit—by a majority that included Chief Justice Roberts—was likely an unusual response to the unique breadth and impact of the climate change regulations.