National Ambient Air Quality Standards, or NAAQS, can be hard enough for states to attain given the sources of air pollution within their own borders.  But add cross-boundary air pollution from upwind states to the mix, and downwind states in particular are left in a real bind: despite their best efforts, these states are unable to control the upwind sources of air pollution that can contribute significantly to their own NAAQS non-attainment.

Some time ago, EPA determined that upwind coal-producing states like Michigan and Kentucky were causing violations of the NAAQS in downwind states like New York and Connecticut.   Based on this finding, EPA issued its Transport Rule, which contained a “good neighbor” provision that authorized the agency to issue federal implementation plans to upwind states (that may have already had effective state implementation plans), requiring them to reduce emissions at an amount reflecting, among other things, their contribution to down-wind state pollution.

Hailed as a huge “win” for EPA and the Obama administration, yesterday the Supreme Court of the United States (“SCOTUS”) upheld EPA’s regulatory authority to issue and implement the good neighbor provision of the Transport Rule.  In its decision, which reversed a D.C. Court of Appeals decision striking down the rule, the SCOTUS acknowledged the technical difficulties the EPA faces in addressing climate change generally, and cross-boundary pollution specifically, and affirmed that judicial deference to the EPA in such matters is most appropriate.

The real loser here? The coal industry—which has argued that EPA’s Transport Rule, and yesterday’s SCOTUS decision, will directly cause the closing of coal power plants in the upwind states.

Next up, EPA is expected to propose a new rule requiring the reduction of carbon dioxide emissions in June.  Under the discretion afforded to the agency in yesterday’s decision, analysts are optimistic that any forthcoming carbon dioxide rule could fend off a similar challenge.

The decision is EPA v. EME Homer City Generation.