U.S. District Court Judge Sharon Gleason on Friday ruled that the administration violated federal law with a proposed road that would split a wilderness area in a national wildlife refuge.
Hours later, Gleason ruled that Trump exceeded his authority when he reversed bans on offshore drilling in vast parts of the Arctic Ocean and dozens of canyons in the Atlantic Ocean.
Environmental groups celebrated the rulings as a judicial check on presidential authority.
"The broader context is that President Trump's lawlessness is catching up with him," said Earthjustice attorney Erik Grafe, who worked on the offshore drilling case. "He and his Interior Department have been treating public lands as if they're gas stations - everything opening up as much as possible as quickly as possible for development, specifically oil and gas development."
U.S. Sen. Lisa Murkowski, an Alaska Republican, said she strongly disagreed with the ruling on Arctic offshore drilling, which asserts that presidents have the power under a federal law to remove certain lands from development but cannot revoke those removals. Only Congress has that authority, the ruling said.
Murkowski said the ruling could have catastrophic impacts for offshore development, which creates jobs, generates revenues and strengthens national security.
"I expect this decision to be appealed and ultimately overturned - if not by the Ninth Circuit, then by the Supreme Court," she said.
Trump is pushing two other oil initiatives in the region - the proposed opening of the coastal plain of the Arctic National Wildlife Refuge to petroleum drilling, and expanding drilling into previously protected parts of the National Petroleum Reserve-Alaska.
Trump has made it clear since taking office that he intended to dismantle the environmental legacy of Barack Obama, the first president to visit the Arctic while in office.
Obama used his authority under the Outer Continental Shelf Lands Act to ban oil drilling in the Chukchi and Beaufort seas off Alaska's north coast with the intent of protecting polar bears, walrus, ice seals and the Native villages that depend on the animals from industrialization and oil spills.
Trump reversed the ban through an executive order as part of a promise to unleash the nation's energy reserves, reduce reliance on foreign oil and spur jobs.
Environmental law and policy experts immediately questioned whether Trump had that authority.
Gleason ruled that he did not.
"The wording of President Obama's 2015 and 2016 withdrawals indicates that he intended them to extend indefinitely, and therefore be revocable only by an act of Congress," Gleason wrote.
In her decision on the Izembek National Wildlife Refuge near the tip of the Alaska Peninsula, Gleason said the proposed road would reverse previous Interior Department policy without providing an explanation.
Murkowski and other Alaska officials have pushed for the road to give residents of the village of King Cove a land route to an all-weather airport for emergency flights. Critics contend other measures are available.
Izembek is internationally recognized habitat for migrating waterfowl. U.S. Fish and Wildlife officials had previously concluded that a road would cause irrevocable damage to the watershed and a land exchange could not compensate for the special qualities of the refuge.
David Raskin, president of Friends of Alaska National Wildlife Refuges, said Monday it would have been the first time that wilderness protections put in place by Congress had been removed so a road could be built.
"This would set a dangerous precedent for all kinds of developments in congressionally designated wilderness," Raskin said.
Gleason is a veteran judge. She was appointed to the Alaska state Superior Court in 2001 and was retained by voters twice before In 2011, Obama made her the first woman appointed to the federal bench in Alaska.
Gleason has overseen other high-profile environmental cases. In 2015, she granted a request by Royal Dutch Shell that activists protesting the company's Arctic offshore drilling plans be ordered to stay away from company vessels.
Two months later, she ruled that Greenpeace USA would be fined $2,500 for each hour its activists blocked a Shell icebreaking ship from leaving Portland, Oregon, by dangling from the St. Johns Bridge over the Willamette River.
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