Members of Utah’s congressional caucus, not content with eviscerating two national monuments in the state, have unleashed a new assault on public lands, proposing legislation that hides an agenda of deregulation behind the shield of the National Park Service and the beloved park system it oversees.

On Dec. 6, two days after President Trump radically reduced the size of the Grand Staircase Escalante and Bears Ears National Monuments by some two million acres, the largest reversion of federal land protections in the nation’s history, Representative Chris Stewart, Republican of Utah, introduced legislation to establish the Escalante Canyons National Park and Preserve.

On its face, the bill might seem like something for advocates of preserving iconic Western landscapes to embrace in the face of Mr. Trump’s rollback. The new park would incorporate a small portion of the original 1.9-million-acre Grand Staircase area that the president’s proclamation fractured. The other three members of the state’s House delegation, all Republicans, signed on as co-sponsors.

But a reading of the bill, H.R. 4558, reveals it as a Trojan horse, appearing as a gift to the public while eroding federal environmental protections on public lands. If it becomes law, the bill could set a precedent with enormous consequences nationally, all of them bad for the national parks and the park service, which celebrates its 102nd birthday this August. It is, in fact, a model for the piecemeal unraveling of the more than 400 national parks, monuments, battlefields, historic sites, recreation areas and other places in the park system.