Supreme Court Rejects EPA Mercury Emissions Rule

On June 29, 2015, the Supreme Court cast serious doubt upon the future of the Mercury and Air Toxics Standards ("MATS") by finding that the Environmental Protection Agency ("EPA") failed to adequately consider the costs of the rule as part of its initial decision to issue the rule under the Clean Air Act ("CAA").¹ MATS is a regulatory regime aimed at reducing emissions of mercury and other pollutants from power plants. MATS would have imposed caps on coal and oil-fired power plants' emissions of mercury, toxic metals, and other pollutants.

While the decision has far-reaching implications, the rule remains in effect, at least temporarily. The Supreme Court did not permanently invalidate the MATS rule, but rather remanded it back to the D.C. Circuit. The D.C. Circuit may now either vacate the rule, or remand it to EPA – intact and in effect – until EPA responds with a sufficient cost evaluation.²