While the Court’s decision marks a symbolic defeat for EPA, it may not significantly alter power plant operators’ compliance efforts.

In a much anticipated decision delivered on the last day of the term, the Supreme Court struck down the Mercury and Air Toxics Standards, or MATS rule because EPA failed to consider costs in determining whether to regulate the power sector. For America’s coal-fired power plants, the decision in Michigan v. EPA may have a limited impact. The rule was not stayed during the four-year judicial review of the rule, and as a result retirement, fuel-switching and upgrade decisions have already been made at many facilities in response to MATS as well as other Clean Air Act (CAA) rules and these decisions may not be reversed due to the increased viability of natural gas-fired power generation.