[JURIST] The US Court of Appeals for the Ninth Circuit [official website] on Wednesday upheld [opinion, PDF] an approval by the Environmental Protection Agency (EPA) [official website] of caps on motor vehicle emissions in California. The court held that no abuse of discretion had occurred, citing the broad discretion which must be afforded to a government agency’s interpretations of its own regulations as its reason for upholding the EPA’s decision. A coalition of environmental groups, including the National Resource Defense Council [official website], originally filed suit alleging the EPA’s determinations were arbitrary, capricious, and contrary to the law because the EPA failed to consider attainment demonstrations of the approved limitations. The coalition was concerned that the caps did not adequately address the issues of air pollution faced by people living in close proximity to California highways. The EPA made the determination of the adequacy of the emissions limits as part of the approval process for a broader state implementation plan relating to transportation. It is unclear whether the coalition will petition the US Supreme Court [official website] for review.

This case stems from the controversial ability of the EPA to control the regulation of greenhouse gases. Last year, the US Senate [official website] defeated a resolution [materials; JURIST report] aimed at limiting the ability of the EPA to regulate greenhouse gas emissions under the Clean Air Act [materials]. The US Supreme Court affirmed the EPA’s ability to regulate carbon emissions under the Clean Air Act in its 2007 ruling in Massachusetts v. Environmental Protection Agency [Cornell LII backgrounder; JURIST report]. In its ruling, the court held that if the EPA could show a link between greenhouse gas emissions and public health and welfare, then the act gives it the power to regulate emissions. The EPA announced last December [JURIST report] that it had found that greenhouse gases “threaten the public health and welfare of current and future generations,” and that emissions from motor vehicles contribute to greenhouse gas pollution.