A federal court ruling that the U.S. Bureau of Land Management had an invalid director for more than a year has cast doubt over several of the agency's efforts to drive oil and gas development on federal lands.

William Perry Pendley, the BLM's deputy director for programs and policy, served unlawfully as the agency's director for more than 400 days because he was not confirmed by the Senate as required by law, according to the ruling last week by U.S. District Judge Brian Morris in Montana.

Morris said "any 'function or duty' of the BLM Director that has been performed by Pendley would have no force and effect and must be set aside." He gave lawyers 10 days to record which decisions by Pendley should be impacted.

The BLM – which is an agency of the Department of Interior that oversees nearly 250 million acres of public lands – regulates interests ranging from mining and oil extraction to recreation and livestock grazing. It has been at the center of the Trump administration’s push to relax environmental regulations for gas and oil drilling and other expansion on public lands.

Pendley finalized many "Resource Management Plans" directing how federal lands are used and developed, including those for two Utah national monuments that Trump reduced soon after taking office – Bears Ears and Grand Staircase-Escalante.

He also backed a plan that ended a ban on oil and gas leases in California.

Calling the ruling "a tsunami," National Audubon Society attorney Nada Culver said, "the court's reasoning makes it pretty clear that a lot of the activities that Mr. Pendley has been involved in have now been invalidated."

A U.S. Department of Interior spokesman called the ruling "outrageous," adding that "we will be appealing this decision immediately."