President Donald Trump brought together two unlikely groups after revoking federal protections on nearly two million acres of land in Utah — Native Americans and paleontologists, who joined together Tuesday to sue him to stop him from opening the land to development and extractive industries.

It was a busy day for the administration’s lawyers: Five Native American tribes, including the Navajo Nation, plus a host of environmental groups filed suit Monday, arguing that the Trump administration’s move to revoke monument status from Bears Ears National Monument and Grand Staircase-Escalante is unconstitutional. Presidents have the ability to designate national monuments and grant them protection from development under the Antiquities Act, but the lawsuits argue that the act doesn’t give presidents the right to roll back those protections once they’ve been issued.

The result of these cases will set precedent: If the courts side with Trump, the future of these protected lands will lay in the hands of Trump, or future administrations, and could be opened up to extractive industries and development at any point down the line.

In addition to the tribes, Earthjustice, an environmental law organization, has filed suit on behalf of themselves and eight other environmental groups, E&E News reports. They’re arguing that only Congress has the authority to revoke monument status.

The lands, the complaint says, “will now be open to harmful developments such as coal mining, new roads, off-highway vehicle abuse, and oil and gas drilling. These types of developments will scar the lands, compromise vital parts of the paleontological record, ruin their wild, natural character, and destroy the resources the Monument was created to protect.”

And a third lawsuit, filed by law firm Covington & Burling LLP on behalf of the Conservation Lands Foundation, Grand Staircase Escalante Partners, and the Society of Vertebrate Paleontology, also claims that the president’s shrinking of the monuments is unconstitutional, according to E&E News.

(The Society of Vertebrate Paleontology has a particularly specific interest in the federal protections — so far, over 20 species of dinosaurs have been discovered in Grand Staircase-Escalante.)

The response was quick following Trump’s announcement Monday that he’d be trimming Bears Ears National Monument by 85 percent, removing 1.1 million acres from federally protected status and splitting it into two separate sections. He’s also looking to cut Grand Staircase-Escalante, another monument, also in Utah, by half, or 800,000 acres.

“They declared war on us today,” Shaun Chapoose, a member of the Ute Indian Tribe Business Committee told the Salt Lake Tribune at the time. “If they think we’re not prepared to protect it, they’re kidding themselves.”

Trump, meanwhile, has framed the move as rolling back federal overreach.

“Your timeless bond with the outdoors should not be replaced with the whims of regulators thousands and thousands of miles away,” Trump said Monday during a speech in Salt Lake City. “I’ve come to Utah to take a very historic action to reverse federal overreach and restore the rights of this land to your citizens.”

“We’ve seen how this tragic overreach has prevented many Native Americans from having a voice on their sacred lands, where they practice their most important ancestral and religious traditions,” he added.