Interest Groups

U.S. Supreme Court Declined Review of Challenge to EPA MATS Rule - Environmental Law News

Get the news you want the way you want it: click the RSS button in the right corner to add this feed to your RSS reader, or click here to subscribe to this content. By subscribing, you’ll find this news on your Member Account page, and the latest articles will be emailed to you in your customized IndyBar E-Bulletin e-newsletter.

Environmental Law News

Posted on: Jun 15, 2016

By Melissa A. Gardner, Taft Stettinius & Hollister LLP

On Monday, June 13, the U.S. Supreme Court declined to review a decision by the D.C. Circuit Court of Appeals upholding the Mercury and Air Toxics Standards (“MATS”) rule promulgated by the EPA.

This matter stems from EPA’s 2012 MATS rule requiring coal and oil-fired power plants to reduce their mercury and other toxic air emissions. The Clean Air Act provides that EPA may regulate emissions of hazardous air pollutants from power plants only if it concludes that the regulation is “appropriate and necessary.” See 42 U.S.C. 7412. In making its determination that the MATS rule was “appropriate and necessary,” EPA did not consider costs. It is on that basis – EPA’s refusal to consider costs – that 23 states and several companies brought their challenge to the MATS rule in the D.C. Circuit Court of Appeals. The D.C. Circuit upheld EPA’s decision to not consider costs. However, the U.S. Supreme Court then granted certiorari to resolve the question and held, on June 29, 2015, that EPA must consider costs in deciding whether it is “appropriate and necessary” to regulate emissions from power plants. Specifically, the Court ruled that EPA had interpreted the Clean Air Act unreasonably when it deemed costs irrelevant to the decision to regulate power plants. As a result, the case was remanded back to the D.C. Circuit. See Michigan v. EPA, 135 S.Ct. 2699 (2015).    

The D.C. Circuit then ruled that EPA’s MATS rule could be left in place while EPA re-analyzed associated costs and cured the defect in its “appropriate and necessary” analysis. 20 states sought certiorari to the U.S. Supreme Court, arguing that the D.C. Circuit should have vacated the rule. It is this petition that was denied by the Court on Monday.

EPA finalized its MATS rule on April 25, by issuing its Supplemental Finding that the costs justified the regulation of such emissions from power plants. This Supplemental Finding can be found online here.

If you would like to submit content or write an article for the Environmental Law Section page, please email Kara Sikorski at


Indianapolis Bar Association (IndyBar) est. 1878 | 4,536 Members (as of 2.11.21)