Michigan v. Environmental Protection Agency
United States Supreme Court
135 S. Ct. 2699 (2015)
The Clean Air Act directed the EPA (defendant) to regulate hazardous air pollutants from power plants if the agency found doing so 'appropriate and necessary.' The EPA promulgated regulations without considering costs at that threshold stage, though it later factored cost into how stringent the regulations would be; the regulations ultimately cost power plants about $10 billion annually. The D.C. Circuit upheld the regulations, and the Supreme Court granted certiorari to review whether ignoring costs at the initial 'appropriate and necessary' stage was reasonable.
Whether agency action under Chevron is reasonable only if it rests on a consideration of all relevant factors, including cost, in deciding whether regulation is appropriate and necessary.