A federal judge has ruled that a controversial Trump official who has overseen a vast weakening of public lands protections cannot continue in his position since he has not been approved by the Senate. US district judge Brian Morris ruled that former oil industry attorney William Perry Pendley had been unlawfully running the Bureau of Land Management (BLM), which oversees nearly one out of every 10 acres of US land, for 424 days. Brett Hartl, government affairs director at the Center for Biological Diversity, argued that as a result, courts could potentially strike down every major BLM action in roughly the last three years. “They’ve never had a valid person running that agency,” said Hartl. “Even before Pendley there was just a never-ending list of rotating acting people, and that’s not what you’re supposed to do.” The US constitution requires Senate approval for agency heads, for which the Federal Vacancies Reform Act sets time limits. The Trump administration nominated Pendley to the post but rescinded the nomination when it became apparent he might not secure enough votes. The BLM decides how nearly a quarter-billion acres of public lands, mainly in the western US, can be used for mining, oil and gas drilling, livestock grazing and recreation. Under Trump, it has been at the forefront in the administration’s drive to loosen environmental restrictions for oil and gas drilling and other development on public lands. Before joining the Trump administration, Pendley called for the government to sell off public lands and claimed climate change did not exist. He has also cited anti-Muslim figures and blamed undocumented migrants for diseases, according to CNN. Under Pendley, the BLM has finalized plans to permit drilling, mining and grazing on the Bears Ears and Grand Staircase Escalante national monuments in Utah, both downsized by Trump. It has proposed oil and gas drilling in Chaco Canyon in New Mexico, a national historic park where Native artifacts have been found. Pendley has also begun moving the bureau from Washington DC to Grand Junction, Colorado – which longtime staff believed was meant to weaken regulatory abilities. All these actions are now under scrutiny. “We haven’t had a decision of this caliber in a long time related to [Department of the] Interior decision making,” said Collin O’Mara, president and chief executive of the National Wildlife Federation. “We’re in uncharted territory.” In July, Montana’s Democratic governor sued to remove Pendley, saying he was illegally overseeing the bureau, which is housed within the interior department. On Friday, the judge gave the department 10 days to submit a brief to the court to determine what decisions by Pendley should be set aside. “Today’s ruling is a win for the constitution, the rule of law, and our public lands,” Governor Steve Bullock said. Environmental groups and Democratic lawmakers from Western states also cheered the judge’s move after urging for months that Pendley be removed. At a Joe Biden campaign event on Saturday, for National Public Lands Day, Senator John Tester of Montana said Pendley “never should have been in that position in the first place”. “This guy has publicly fought for selling off our public lands and President Trump thought he was the best person to be put in the position to be in charge of our 245 million acres of public lands.” “Quite frankly,” Tester said, “[Trump] doesn’t give a damn about our public lands.” Biden opposed Pendley’s nomination. “Today is Public Lands Day and National Hunting and Fishing Day,” the Democratic nominee said on Twitter, “and what better way to celebrate than the long overdue removal of William Perry Pendley … a victory for everyone who values our public lands over those who want to exploit them for profit.” Interior spokesman Conner Swanson said the administration would appeal and called the decision “outrageous” and “well outside the bounds of the law”. He said the Obama administration had similarly filled key posts at the agency with temporary authorizations. (Other administrations have overshot deadlines to seek confirmation from the Senate, but environmental advocates say none have ignored them repeatedly as Trump has.) Environmental groups have challenged acting leadership in other parts of the interior department – at the National Park Service, the Fish and Wildlife Service and the Office of Surface Mining. The decision is the latest pushback against the administration’s practice of filling key positions without obtaining Senate approval. Last month, the Government Accountability Office, a bipartisan congressional watchdog, said acting Department of Homeland Security secretary Chad Wolf and his acting deputy, Ken Cuccinelli, were improperly serving and ineligible to run the agency. It has been at the forefront of administration initiatives on immigration and law enforcement. Shortly after the GAO questioned the DHS officials, Trump formally nominated Wolf. The Senate held a hearing last week but is unlikely to confirm him before the November election. Trump pulled Pendley’s nomination when it became clear it could disrupt key Senate races in Montana, where Bullock is seeking to unseat the Republican Steve Daines, and Colorado, where the Republican Cory Gardner is challenged by a former governor, John Hickenlooper. Public lands enjoy popular support in those states. Pendley held on to the post despite the withdrawal of his nomination, under an arrangement he himself set up. In a 22 May order, Pendley made his position, as deputy director, the top post at the bureau while the director’s office was vacant. After that he approved two sweeping land resource management plans in Montana that would open 95% of federal land in the state to oil and gas development, Bullock’s attorneys contended in court filings.