In considering the most serious efforts to date to invalidate the federal climate change regulations, the U.S. Court of Appeals for the D.C. Circuit unanimously upheld several of EPA’s Clean Air Act greenhouse gas (GHG) emissions rules against a challenge by industry groups and several states. In the case, Coalition for Responsible Regulation, Inc., et al. v. EPA, No 09-1322, the Court noted that considerable deference to agency scientific expertise was appropriate, and that EPA had taken steps to ease the potential regulatory burden on the challengers.

At issue were a series of three related EPA actions in response to Massachusetts v. EPA, the Supreme Court’s landmark 2007 decision requiring EPA to assess GHGs as air pollutants under the Clean Air Act. The first was EPA’s Endangerment Finding, which concluded that GHGs may “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.” The Court noted that “EPA had before it substantial record evidence that anthropogenic emissions of greenhouse gases ‘very likely’ caused warming of the climate over the last several decades.” This “substantial” scientific evidence was adequate to support the Endangerment Finding, particularly in light of the “precautionary and preventative orientation” of the Clean Air Act.