This bill would change how air quality standards are enforced in the United States. Under this bill, states could avoid federal penalties and “nonattainment” designations for air pollution if they can prove that most of the pollution comes from outside the U.S., from exceptional events like wildfires, or from mobile sources—such as traffic—that are difficult for the state to control. This means that if a state demonstrates it would meet federal air quality standards except for these uncontrollable sources, federal sanctions and stricter regulations would not apply.