(CN) Legal challenges to the Trump administration’s 2017 decision to downsize and develop on Utah’s Bears Ears and Grand Staircase-Escalante national monuments will move forward, a judge has ruled, handing environmental and tribal groups their first victory in the case.

In 2017, President Donald Trump ordered the shrinking of Bears Ears National Monument by 85 percent, slicing the 1.3 million acres designated by President Barack Obama a year earlier to about 200,000 acres. The Bureau of Land Management’s final plan would open Bears Ears to target shooting, development of roads and utility lines, vegetation removal and allow for an ATV route through culturally rich and scenic areas.

The area is undeveloped wilderness co-managed by BLM and the U.S. Forest Service, in coordination with five tribal groups, including the Navajo Nation.

Trump also ordered cuts to Grand Staircase-Escalante National Monument, shrinking its 1.8 million acres by 47 percent. In addition to its natural beauty, the monument designated by Bill Clinton in 1996 is home to dinosaur fossils from over 75 million years ago that were discovered in 2000.

Three challenges were filed days after the administration announced its plans for the Utah monuments, with plaintiffs ranging from conservation groups, tribal nations and environmental advocacy groups. U.S. District Judge Tanya Chutkan of the District of Columbia consolidated the cases.

The Trump administration moved to dismiss, claiming the plaintiffs lacked standing, their cases weren’t ripe for adjudication and that the president has the right to chop the monuments under the Antiquities Act – the law passed by Congress vesting the executive branch with the power to create monuments and national parks.

But on Monday, Chutkan denied the motion noting the plaintiffs will need to file an amended complaint to address “the impending release of a series of new management plans regarding Bears Ears National monument.” She ordered the parties to come prepared to discuss “an expedited, coordinated schedule for the filing of an amended complaint and the subsequent briefing” at a status conference Oct. 7.

Natural Resources Defense Council senior attorney Kate Desormeau said, “We’re pleased that our challenges to the Trump administration’s illegal monument rollbacks are moving forward, and we look forward to proving our case on the merits.”

In a statement, Southern Utah Wilderness Alliance legal director Stephen Bloch said, “We intend to pursue these cases until these remarkable cultural, scientific and wild red rock landscapes are restored to their full glory.”

Taylor McKinnon with the Center for Biological Diversity said, “This ruling brings us one step closer to justice for Trump’s brutal attack on national monuments”

In a statement, the Department of the Interior said it supports “Trump’s decisions and remains confident that the court will agree after receiving an expanded briefing.”

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