California Attorney General Xavier Becerra sued the Environmental Protection Agency Tuesday for withdrawing a policy that imposed strict limits on hazardous air pollutants from factories, plants, and other types of facilities considered “major” polluters.

Under the “once-in-always-in” policy, established in 1995, major polluters failing to meet certain emission thresholds were required to meet those standards from then on, even if the facility made changes to reduce its pollution.