President Trump traveled to Utah Monday to sign a pair of proclamations that collectively trim the size of two national monuments designated by the Obama administration by more than two million acres, including one in an area of some oil and gas drilling, in a move that represents the largest rollback of protected federal land in the nation’s history.

The White House said Trump signed a proclamation to reduce the size of the Bears Ears National Monument by 83% from 1.35 million acres to 228,784 acres and to two units, Shash Jáa (measuring 129,980 acres) and Indian Creek (71,896). Trump also signed a proclamation to reduce the Grand Staircase-Escalante National Monument in southern Utah from 1.88 million acres to about 1 million acres, a 46% reduction and to three units: Grand Staircase (measuring 209,993 acres), Kaiparowits (551,034) and Escalante Canyons (242,836).

“No one values the splendor of Utah more than the people of Utah, and no one knows better how to use it,” Trump said. “The Antiquities Act does not give the federal government unlimited power to lock up millions of acres of land and water, and it’s time we ended this abusive practice. Public lands will once again be for public use.”

The administration said previous administrations abused the Antiquities Act, and sometimes made monument designations against the will of the local public.

The energy industry praised the move. “By resizing and reshaping the monument, President Trump will rightfully return decision-making power to the people for which Bears Ears (now Shash Jáa and Indian Creek) has the most significance,” said Institute for Energy Research President Thomas Pyle. “Energy development, land stewardship and recreation are all important considerations and this decision reflects that.”

But environmental groups were outraged and hinted that legal action may be forthcoming.

“The Antiquities Act does not give the president the legal authority to eliminate or reduce a national monument — a power exclusively delegated to the U.S. Congress,” said Sierra Club’s Ashley Soltysiak, director of the Utah chapter. “This is yet another pathetic example of Trump’s continued abuse of power in support of special interests.”

Soltysiak said when Grand Staircase was formed in 1998, it “was amenable to a land exchange for mineral extraction; it appears that it did not satiate special interests’ greed…Replacing recreational landscapes with drilling pads, machinery, and public restriction stands to devastate thriving and emerging businesses and the people they support.”

The Trump administration pushed back, saying that it was a myth that previous administrations had not reduced the size of national monuments.

“Monuments have been reduced at least 18 times under presidents on both sides of the aisle,” the Department of Interior (DOI) said. “Some examples include President John F. Kennedy excluding Bandelier National Monument; Presidents Taft, Wilson, and Coolidge reducing Mount Olympus National Monument; and President Eisenhower reducing the Great Sand Dunes National Monument in Colorado.”

Last April, Trump signed an executive order ordering the DOI to review any national monument designation of more than 100,000 acres made since Jan. 1, 1996. The original review affected 27 national monuments, but six were later removed. Of the remaining 21, 16 were in the onshore, and all but Maine’s Katahdin Woods and Waters are in the West. The remaining five are marine monuments in the offshore.

From the start, Bears Ears in San Juan County, UT, appeared to be the most controversial designation. President Obama set aside land for the monument last December, shortly before leaving office. The area has seen mostly conventional but also some unconventional oil and gas drilling. San Juan County also overlays theParadox Basin, which includes the Cane Creek and Hovenweep shales.

In an interim report filed in June, DOI Secretary Ryan Zinke recommended that Bears Ears be trimmed in size but did not specify by how much. Two months later, Zinke submitted a draft report to Trump that reportedly recommended the president reduce the size of Bears Ears, Grand Staircase and the Cascade-Siskiyou National Monument, which straddles southwest Oregon and northwest California.

A 19-page memo from Zinke to Trump was leaked to the media in September. The memo listed recommended changes at 10 national monuments, including trimming the size of Bears Ears and Grand Staircase, but it did not specify any area reductions.