A group of environmental and conservation groups sued President Donald Trump and Interior Secretary Ryan Zinke in federal court on Monday, alleging that Trump did not have the authority to dramatically shrink Utah’s Grand Staircase-Escalante National Monument.

The lawsuit, which comprises The Wilderness Society, the Natural Resources Defense Council, the Sierra Club and seven other groups as plaintiffs, argues that Trump’s decision to reduce the size of Grand Staircase-Escalante was “unlawful” and “exceeds his authority under the U.S. Constitution and the Antiquities Act.”

The White House did not immediately respond to a request for comment. Heather Swift, a spokeswoman for the Interior Department, said: “We are well within our authority,” and referred further questions to the Department of Justice.

A group of Native American tribes in Utah was expected to file a similar suit against Trump and his administration in federal court on Monday over his decision to dramatically shrink Utah’s Bears Ears National Monument. The suit will come from representatives from the Hopi, Zuni, Ute Mountain Ute, the Navajo Nation and the Ute Indian tribe, lawyers for the tribes said.

Trump had announced on Monday in Salt Lake City that he would follow Zinke’s recommendations and reduce Bears Ears National Monument by over 80 percent and Grand Staircase-Escalante National Monument by roughly 45 percent. The two presidential proclamations, which Trump signed at an event at the Utah Capitol, would break Bears Ears into two national monuments and Grand Staircase-Escalante into three separate monuments.

Trump said his decision was made to “reverse federal overreach and restore the rights of this land to your citizens.”

“The families and communities of Utah know and love this land the best, and you know the best how to take care of your land. You know how to protect it. And you know best how to conserve this land for many, many generations to come,” the President said.

Largely ignoring the tribes who oppose the decision, Trump framed the fight as one between local officials and bureaucrats in Washington, who he said “don’t care for your land like you do.”

The lawsuit, filed in the US District Court for the District of Columbia, outlines why the plaintiffs believe Grand Staircase-Escalante should be protected, arguing that the order “exceeds his authority under the Antiquities Act.”

“The Act authorizes Presidents to create national monuments; it does not authorize Presidents to abolish them either in whole or in part, as President Trump’s action attempts to do,” reads the filing.

The Antiquities Act, a presidential power that was first signed by President Teddy Roosevelt in 1906, gives the President the power only to designate a monument, not revoke it, the plaintiffs argue. Additionally, the lawsuit argues that Trump’s order violates the separation of powers because Congress has the right to change national monuments created under the Antiquities Act.

“Grand Staircase is a cradle of biodiversity, and losing even an acre would be a crime,” said Taylor McKinnon of the Center for Biological Diversity, a plaintiff in the case. “We must protect this monument’s wildlife, stunning landscapes and cultural treasures for future generations. Trump and the fossil-fuel industry have picked the wrong battle.”

Though environmental groups have also protested Trump’s decision on Bears Ears and plan to file their own suits, it is intentional that the five tribes will file the first lawsuits against the Trump administration for that monument.

“The tribes feel it was important to file first, to be ahead of the line, to make it very clear that this is not just a conservation issue,” said Natalie Landreth, a senior staff attorney at the Native American Rights Fund, a group representing the Hopi, Zuni and Ute Mountain Ute in the lawsuit. “To them, it is a tribal sovereignty issue.”

Trump administration officials have long expected that Trump’s proclamations would end up in court, given that environmental groups and tribes had pledged to do so.

Zinke, speaking with reporters aboard Air Force One on Monday before the lawsuit was filed, accused “special interests” of polarizing the issue and said he isn’t going to shy away from any legal challenge.

“I don’t yield to pressure, only higher principle. And I don’t think public policy should be based on the threat of lawsuit,” he said.

He added that the changes have been revised by Interior Department solicitors and approved.

“I feel confident in the Department of Justice,” Zinke added. “And I feel confident that we will prevail because it’s the right thing to do.”