President Donald 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, a US judge has said in a ruling that restored the Obama-era restrictions.

US District Court Judge Sharon Gleason in a decision late on Friday threw out Trump’s executive order that overturned the bans that comprised a key part of Obama’s environmental legacy.

Presidents have the power under a federal law to remove certain lands from development but cannot revoke those removals, Gleason said.

Endangered polar bears don’t need to fear oil drillers as a result of the ruling, but seals will always have something to worry about. Photo: AP

“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,” said Gleason, who was nominated to the bench by Obama.

A Department of Justice spokesman, Jeremy Edwards, declined to comment on Saturday.

The American Petroleum Institute, a defendant in the case, disagreed with the ruling.

“In addition to bringing supplies of affordable energy to consumers for decades to come, developing our abundant offshore resources can provide billions in government revenue, create thousands of jobs and will also strengthen our national security,” it said in a statement.

Erik Grafe, an attorney with Earthjustice, welcomed the ruling, saying it “shows that the president cannot just trample on the Constitution to do the bidding of his cronies in the fossil fuel industry at the expense of our oceans, wildlife and climate.”

Earthjustice represented numerous environmental groups that sued the Trump administration over the April 2017 executive order reversing the drilling bans. At issue in the case was the Outer Continental Shelf Lands Act.

In 2015, Obama halted exploration in coastal areas of the Beaufort and Chukchi seas and the Hanna Shoal, an important area for walrus. In late 2016, he withdrew most other potential Arctic Ocean lease areas – about 98 per cent of the Arctic outer continental shelf.

The bans were intended to protect polar bears, walruses, ice seals and Alaska Native villages that depend on the animals.

In the Atlantic, Obama banned exploration in 5,937 square miles (15,377sq/km) of underwater canyon complexes, citing their importance for marine mammals, deep-water corals, valuable fish populations and migratory whales.