Massachusetts V. Environmental Protection Agency - Opinion of The Court

Opinion of The Court

First, the petitioners were found to have standing. Justice Stevens reasoned that the states had a particularly strong interest in the standing analysis. The majority cited Justice Holmes' opinion in Georgia v. Tennessee Copper Co.:

"The case has been argued largely as if it were one between two private parties; but it is not. The very elements that would be relied upon in a suit between fellow-citizens as a ground for equitable relief are wanting here. The State owns very little of the territory alleged to be affected, and the damage to it capable of estimate in money, possibly, at least, is small. This is a suit by a State for an injury to it in its capacity of quasi-sovereign. In that capacity the State has an interest independent of and behind the titles of its citizens, in all the earth and air within its domain. It has the last word as to whether its mountains shall be stripped of their forests and its inhabitants shall breathe pure air."

Second, the Court held that the CAA gives the EPA the authority to regulate tailpipe emissions of greenhouse gases. The CAA provides:

“The Administrator shall by regulation prescribe (and from time to time revise) in accordance with the provisions of this section, standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”

The CAA defines "air pollutant" as "any air pollution agent or combination of such agents, including any physical, chemical, biological, radioactive . . . substance or matter which is emitted into or otherwise enters the ambient air". The majority opinion commented that "greenhouse gases fit well within the CAA’s capacious definition of air pollutant."

Finally, the Court remanded the case to the EPA, requiring the agency to review its contention that it has discretion in regulating carbon dioxide and other greenhouse gas emissions. The Court found the current rationale for not regulating to be inadequate and required the agency to articulate a reasonable basis in order to avoid regulation.