On August 21, 2012, the U.S. Court of Appeals for the District of Columbia Circuit overturned a U.S. Environmental Protection Agency rule, known as the Cross-State Air Pollution Rule (CSAPR), which required 28 states in the East, Midwest and South to reduce power plant emissions that cross their state borders. CSAPR was intended to help downwind states meet national ambient air quality standards (NAAQS) for ozone and fine particulate matter. The result of this decision could prod the EPA into giving greater deference to states in adopting plans to achieve and maintain the NAAQS.

The challengers of CSAPR include industry groups, a coalition of more than a dozen states, including Ohio, Michigan and Texas, and other stakeholders.

The CSAPR rule required states to reduce nitrogen oxide and sulfur dioxide emissions from power plants whose emissions travel downwind and result in preventing the downwind states from meeting the NAAQS. However, the rule established emissions reductions based on the costs of the reductions rather than on the amount of pollution that each upwind state was contributing. The court held the rule invalid because it may require upwind states to reduce their emissions by more than their “significant contributions” to a downwind state’s nonattainment with the NAAQS. Additionally, the court said the EPA’s rule violated the Clean Air Act since it did not allow the states an opportunity to submit their own implementation plans by which NAAQS would be met and maintained.

The D.C. Circuit Court decision vacates the CSAPR in its entirety, leaving the Bush administration’s less-stringent 2005 Clean Air Interstate Program in place until the EPA develops a valid replacement.

The EPA must decide within the next few weeks whether it will seek a rehearing before a different panel of judges or appeal the decision.