SALT LAKE CITY — President Donald Trump on Monday took the rare step of scaling back two sprawling national monuments in Utah, declaring that “public lands will once again be for public use” in a move cheered by Republican leaders who lobbied him to undo protections they considered overly broad.

The decision marks the first time in a half century that a president has undone these types of land protections. Tribal and environmental groups oppose the decision and began filing lawsuits Monday in a bid to stop Trump and Interior Secretary Ryan Zinke.

Trump made the plan official during a speech at the State Capitol, where he signed proclamations to shrink the Bears Ears and Grand Staircase-Escalante national monuments. State officials said the protections were overly broad and closed off the area to energy development and other access.

Environmental and tribal groups say the designations are needed to protect important archaeological and cultural resources, especially the more than 1.3 million-acre (2,030-square-mile) Bears Ears site featuring thousands of Native American artifacts, including ancient cliff dwellings and petroglyphs.