SCOTUS reverses Fourth Circuit's Duke Energy Decision

In Environmental Defense v. Duke Energy, SCOTUS examined whether Duke violated the Clean Air Act when it failed to get a permit before updating its coal plants in the Carolinas. The Fourth Circuit and the District Court found in favor of Duke and held that no permit was required inasmuch as hourly emissions from Duke's plants in North and South Carolina would not increase. Environmental groups had argued that federal law requires utilities to install anti-pollution equipment if they make plant modifications that change their annual--not hourly--emissions of nitrogen oxides, sulfur dioxide, and other pollutants.

The Justices agreed with the environmental groups, holding that requiring the use of an hourly emissions rate would essentially invalidate EPA rules dating back to 1980.