Editor's Summary: On July 11, 2008, the U.S. Court of Appeals for the District of Columbia Circuit rejected one of EPA's major CAA rulemaking initiatives--the Clean Air Interstate Rule (CAIR). The ruling came as a surprise to both environmental groups and industry alike, and has, at least temporarily, thrown the status of air quality regulation for several key air pollutants in the eastern United States into disarray. The following Article discusses the decision, the current status of EPA's NAAQS, and the potential impacts the CAIR ruling may have on the future of air quality regulation.