“Some people think that the natural resources of Utah should be controlled by a small handful of very distant bureaucrats located in Washington. And guess what? They’re wrong,” said Trump, speaking in front of the Utah state capitol building.

Bears Ears was created after half a decade of lobbying by five indigenous tribes: the Hopi, the Navajo, the Ute, the Ute Mountain Tribe, and the Zuni. The nations had long sought special status for the land, which all five consider sacred. But when talks broke down with Utah lawmakers several years ago, they pressed Obama to protect the buttes through a national monument.

The five tribes have promised to sue the Trump administration, asserting that the president does not have the right to shrink national monuments. Environmental groups, united in anger at the president’s actions, have also said they will sue to preserve Grand Staircase–Escalante at its current size.

National monuments make for a strange kind of federal land designation. Locals can generally hike, camp, hunt, and fish on national monuments. They cannot mine coal or drill for oil. Grand Staircase–Escalante is known to contain coal reserves. Ryan Zinke, the secretary of the interior, said before the speech that that didn’t play into the president’s decision.

The Antiquities Act was passed in 1906 to enable presidents to protect indigenous archaeological or cultural sites. The law clearly grants the president the right to create new national monuments. But some conservative legal scholars argue that it also contains an implicit right to revoke or revise the size of national monuments.

Presidents have slashed the size of national monuments twice before. During World War I, Woodrow Wilson slashed land from Mount Olympus National Monument to secure lumber rights. The monument was later returned to its largest size and protected as a national park. Franklin Roosevelt also cut the size of Grand Canyon National Monument to open up more land for ranching.

But neither of those reductions were tested in court—and neither occurred during the modern era of environmental law.

Since its passage last century, presidents have activated the law 157 times to protect Native sites, natural wonders, historical landmarks, and vast stretches of seafloor. Congress later enshrined dozens of those monuments—including Grand Canyon, Bryce, Zion, Acadia, and Grand Teton—as national parks, which have an added level of protection.

“This law requires that only the smallest necessary area be set aside for special protection as national monuments,” said Trump, referring to the Antiquities Act.

“Unfortunately, previous administrations have ignored the standard and used the law to lock up hundreds of millions of acres of land under government control. It did so over the loud objections of the people of this state and their elected representatives,” he said.