Story highlights Suit argues Trump exceeded his authority in reducing Grand Staircase-Escalante

Administration officials had expected the proclamations to wind up in court

Salt Lake City (CNN) A group of Native American tribes filed suit against President Donald Trump and a host of administration officials on Monday, alleging that Trump's decision to significantly shrink Bears Ears National Monument is "in violation of the United States Constitution and the Antiquities Act of 1906."

Representatives from the Hopi, Zuni, Ute Mountain Ute, the Navajo Nation and the Ute Indian tribes accused Trump of exceeding "the limited authority delegated to his office," violating "the Antiquities Act and the separation of powers established in the Constitution" and circumventing the law by "attempting to evade that strict limitation" of his power.

The lawsuit, the first against Trump's decision to shrink the monument, comes at the same time that a group of environmental and conservation organizations sued Trump and Interior Secretary Ryan Zinke for dramatically shrinking Utah's Grand Staircase-Escalante National Monument.

That 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 US 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.

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