Udall introduced a bill into the Senate that would reaffirm and enhance protections for national monuments and the procedures for altering them.
President Donald Trump ordered a review of recent and large national monuments during his first months in office, and in late 2017 shrunk two controversial monuments by nearly 90 percent, a move criticized by Udall, some tribes and environmental groups.
Udall's bill, the Antiquities Act of 2018, would reaffirm that while national monuments are created by presidential proclamation, only Congress can modify monument designations. The bill officially declares support for the 51 monuments established between 1996 and 2017.
"President Trump's unprecedented attack on public lands is not just an affront to the overwhelming majority of Americans who cherish these precious places -- it's also illegal," Udall said in the press release.
The bill would also demand that presidentially designated national monuments be surveyed, mapped and management plans be completed within two years. The Rio Grande del Norte National Monument was created by former president Barack Obama in 2013. Nearly five years later, the management plan has yet to be completed although the Taos field office of the BLM is looking to release a draft this spring.