Environmental groups have asked a judge to overturn the sale of drilling rights on public land in Colorado and Utah, saying the Trump administration didn't consider the potential threat to public health and the environment.
A lawsuit filed Thursday in Denver federal court seeks to reverse oil and gas leases on 184 square miles (476 square kilometers) of land.
The suit alleges the U.S. Bureau of Land Management sold the leases without properly reviewing how much air pollution the drilling would cause.
The agency said it had no comment.
The lawsuit was filed by Rocky Mountain Wild, National Parks Conservation Association, Center for Biological Diversity and WildEarth Guardians.
They argue that drilling will worsen ground-level ozone in the area, which they say already exceeds federal standards.