audio_analysisOn March 25, the Supreme Court heard oral argument in three consolidated cases: Michigan v. EPA, Utility Air Regulatory Group v. EPA, and National Mining Association v. EPA. At issue is the quality of the air we breathe.

The Clean Air Act requires the EPA to regulate hazardous air pollutants. For most polluters, the EPA automatically has the ability to regulate. However, if the polluter is a power plant, the EPA can only regulate it if doing so would be “appropriate and necessary” based on a study the agency conducts on the hazards to public health. In 2012, the EPA promulgated a rule regulating the emission of mercury by power plants. The EPA’s study had found that mercury was “highly toxic,” “a threat to public health and the environment,” and that power plants were the largest source of mercury emissions in the United States. Thus, the agency concluded that a regulation was appropriate and necessary.

Business groups and state governments challenged the rule in the D.C. Circuit, arguing that the EPA needed to consider the cost of the regulation when deciding if it was appropriate and necessary. The D.C. Circuit upheld the rule. The Supreme Court granted certiorari to decide whether the refusal to consider costs was unreasonable.