A federal judge has ruled that an executive order by President Donald Trump that lifted a Barack Obama-era ban on oil and gas drilling in the Arctic Ocean and parts of the North Atlantic coast was unlawful, in a major legal blow to Trump's push to expand offshore oil and gas development.

The decision, by Judge Sharon L. Gleason of the United States District Court for the District of Alaska, concluded late on Friday that Obama’s 2015 and 2016 withdrawal from drilling of about 120 million acres of Arctic Ocean and about 3.8 million acres in the Atlantic “will remain in full force and effect unless and until revoked by Congress”. She wrote that an April 2017 executive order by Trump revoking the drilling ban “is unlawful, as it exceeded the President’s authority.”

The decision, which is expected to be appealed in the Ninth Circuit Court of Appeals, immediately reinstates the drilling ban on most of the Arctic Ocean off the coast of Alaska, a pristine region home to endangered species including polar bears and bowhead whales where oil companies have long sought to drill. Along the Atlantic coast, it blocks drilling around a series of coral canyons that run from Norfolk, Virginia, to the Canadian border which are home to unique deepwater corals and rare fish species.

In addition, Friday’s ruling by the judge, an Obama appointee, has broader implications for Trump’s effort to push drilling across the American coastline and on public land.

Specifically, the Arctic Ocean drilling case could give legal ammunition to opponents of Trump’s efforts to roll back protections for two million acres of national monuments created by Obama and President Bill Clinton.

The case adds to a growing roster of legal losses for Trump’s efforts to undo Obama’s environmental legacy. Experts in environmental law estimate that the Trump administration has now lost about 40 environmental cases in federal courts.

Most immediately, the decision will force the interior department to withdraw the waters of the Arctic Ocean from its forthcoming plan detailing where the federal government intends to lease federal waters to oil companies for offshore drilling. A draft of that plan published last year called for drilling off the entire US coastline.

The White House referred questions on the matter to the interior department, where a spokesperson declined to comment.

Although Friday’s court decision relates specifically to a law on offshore drilling, it could also hamstring Trump’s efforts to erase or reduce the creation of large protected areas of public land by previous Presidents.

“The statutes and the Supreme Court have been silent on the authority of a President to modify or reduce a predecessor’s protections of these public land, waters and monuments,” said Patrick Parenteau, a professor of environmental law at Vermont Law School. “But these decisions are showing that if a President wants to reverse a predecessor’s environmental policy, they have to give a cogent reason why. Just saying ‘energy dominance’ is not enough. Saying ‘I won the election’ is not enough.”

Professor Parenteau predicted that the case was likely to reach the Supreme Court, though probably not for several years.

Environmental groups welcomed Friday’s court decision.

“Since coming into office, Trump has been on a one-man campaign to undo the work of his predecessor,” said Niel Lawrence, a lawyer with the Natural Resources Defence Council, who took part in the oral arguments in the Alaska case. “What this opinion confirms is that there are constitutional limits to that.”

Erik Milito, a spokesperson for the American Petroleum Institute, which lobbies for the oil industry and which joined the Trump administration’s case, said: “While we disagree with the decision, our nation still has a significant opportunity before us in the development of the next offshore leasing plan to truly embrace our nation’s energy potential and ensure American consumers and businesses continue to benefit from US energy leadership.”