Massachusetts v. EPA
Plaintiff files a rulemaking petition to ask EPA to regulate greenhouse gasses from new motor vehicles under section 202 of the Clean Air Act. EPA requested public comment on the issue, and received more than 50,000 comments. The EPA decided not to undertake a rulemaking because it felt it was not mandatory for it to do so, and even if it was, this was not the right time to do so.
The court says that although in Heckler court, the refusal to initiate enforcement proceedings is not ordinarily subject to review, there is still some debate to if refusal to regulate can be subject to review.
The court thinks that 555(e) of the APA does allow for judicial review of non-enforcement of rulemaking, but this review is "extremely limited" and "highly deferential."
The court then goes on to the merits and decides that EPA "has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change ... Its action was therefore arbitrary, capricious, ... or otherwise not in accordance with the law."