What Comes Next For Mercury Emissions From Power Plants?

The U.S. Supreme Court held this morning that the U.S. Environmental Protection Agency (EPA) acted unreasonably when it determined in 2000, and again in 2012, that it was "appropriate and necessary" to regulate mercury emissions from coal-fired power plants. The central flaw in EPA's reasoning, the Court held, is that the agency failed to consider the cost of regulation when making the threshold determination that regulation was "appropriate." Under Section 112 of the federal Clean Air Act, EPA must conclude that it is "appropriate" to regulate power plant mercury emissions before it can actually regulate those emissions.

The immediate effect of today's decision is that the ongoing challenge to EPA's mercury regulations will be remanded to the U.S. Court of Appeals for the D.C. Circuit, which previously upheld those regulations. The D.C. Circuit will then face a choice: Should it vacate the regulations, or should it leave them in place while giving EPA additional