 -- Environmental groups and five Native American tribes have filed two lawsuits to block the Trump administration's plan to drastically scale back two national monuments in Utah.

President Donald Trump announced the decision on Monday at the Utah State Capitol. Opponents immediately vowed to take legal action to block the changes.

On Tuesday, a coalition of five tribes filed a complaint in D.C. District Court, arguing the president did not have the authority to undo or replace the existing Bears Ear National Monument. The tribes have long argued that the land protected by President Barack Obama is an important part of their heritage and includes historic and culturally significant artifacts.

The team of lawyers representing the Navajo Nation, Hopi tribe and others is asking the court for an immediate injunction on the Trump decision to prohibit so that the new monuments boundaries cannot be enforced until the matter can be fully litigated.

Shaun Chapoose, a leader from the Ute tribe who is part of the coalition, said at a press conference Monday the announcement was a line in the sand.

"We gathered as sovereign tribes and put aside our differences to benefit not just us but the citizens of the United States. So with that same mentality we'll do the same to protect it. And if they think we're not prepared to protect it they're kidding themselves," Chapoose said.

In a second lawsuit environmental and conservation groups, including the Sierra Club, Natural Resources Defense Council and The Wilderness Society, formally sued the administration for its plans to reduce the size of a second national monument: Utah's Grand Staircase-Escalante.

Both lawsuits say the president doesn't actually have the legal authority to make the changes he announced this week.

Trump authorized a review of national monuments designated under the Antiquities Act in an executive order signed in April. The Antiquities Act was enacted in 1906 and gives the president the power to create national monuments, but there has been some disagreement over whether the act gives the president the authority to eliminate them.

The Congressional Research Service wrote a report on this issue in 2016 that found that while the Antiquities Act doesn't specifically grant the president the power to shrink or eliminate monuments, it does say that monument size "shall be confined to the smallest area compatible with the proper care and management of the objects to be protected," which could be used to justify making the monument smaller.

Trump said Monday that previous administrations abused the act by designating monuments that were too big and gave too much power to the federal government. When he signed the order initiating the review, he called them a "massive federal land grab."

"Previous administrations have ignored the standard, and use the law to lock up hundreds of millions of acres of land and water under strict government control. These abuses of the Antiquities Act give enormous power to faraway bureaucrats at the expense of the people who actually live here, work here, and make this place their home," Trump said in his remarks at the Utah State Capitol.

Interior Secretary Ryan Zinke said Monday the land will still be federal land managed by the Forest Service and Bureau of Land Management. But Republicans on the House Committee on Natural Resources introduced a bill Monday that would establish co-management of the entire area that is no longer part of the monuments between Native American groups and elected officials. The bill's cosponsors, who are all Republicans from Utah, said on a call with reporters Tuesday the legislation will create specific protections around the land that is no longer part of the monument and they hope it will make the lawsuits irrelevant.

In response to a question about the new legislation, Ethel Branch, Attorney General for the Navajo Nation replied: "Then why they are so insistent on the president messing with the original proclamation?"

"Why don't they just honor the existing lawful proclamation instead of doing whatever it is they are trying to do here?"

Rep. Chris Stewart, R-Utah, also said on the call that they will propose creating a national park on the land called Grand Escalante Canyon National Park and will move to transfer Hole in the Rock Road, which is a historic location for the Mormon community in Utah, back to the state's control.

Big names like Patagonia are also getting involved. Patagonia's website Monday featured a page that read "The President Stole Your Land" with information about the president's decision and a call to help groups that are suing the administration.

But Zinke said on a call with reporters Tuesday that no land has been transferred out of federal control and that special interests were using the announcement to raise money.

"The argument that somehow President Trump stole land is nefarious, false and a lie," Zinke said Tuesday.

One of the concerns cited by those who want the monuments to stay as they are is that revoking the monument status will allow companies to begin mining the land for oil, gas or uranium.

“The Trump administration has declared 'open season' on places Americans hold dear so that profit-seekers can drill, mine and log our public lands for private gain. By making commercial exploitation of these national treasures the top priority, this administration betrays the history of these sacred places, as well as their value as places for people to enjoy the outdoors and for wildlife to thrive," Wilderness Society President Jamie Williams said in a statement.

The bill introduced would also protect the land from mining, Republican Rep. John Curtis of Utah said on a call with reporters, as well as require a law enforcement presence and a unit specifically to protect the antiquities and historical sites on the land.

An Interior Department official said Monday that there has not been any interest in mining on land that was part of the monuments. The Bureau of Land Management announced last week that there will be an auction in March to allow oil and gas permits in other parts of San Juan County, where the monuments are, and a neighboring county. Local political leaders cited harm to the mining industry as a reason the monuments should be made smaller in a comment posted on the review in May.

A hearing has not yet been scheduled in either of the lawsuits.