Under pressure from gun rights groups and about half of the U.S. Senate, the Interior Department has agreed to rewrite its regulations to comply with state laws.
Utah, like much of the West, allows guns in state parks. So the change would make it legal for those traveling through Arches or Zions to take along a loaded gun.
The current regulations require visitors to keep their guns unloaded and stowed.
Utah Sens. Orrin Hatch and Bob Bennett joined 45 other colleagues, most of whom are Republicans, in asking Interior Secretary Dirk Kempthorne to make the change.
The Bureau of Land Management and U.S. Forest Service rules allow loaded guns, while the National Parks and U.S. Fish and Wildlife do not.
The letter said the regulations "infringe on the rights of law-abiding gun owners" and are "confusing, burdensome and unnecessary."
Kempthorne agreed to rewrite the rules by April 30. The new regulation will then be available for public comment.
Bennett said he supports Kempthorne's "efforts to update firearm policies." Hatch declined to comment.
The National Rifle Association has long fought to change the firearm rules, saying it is a matter of self-protection. But a number of ranger groups and conservationists protest.
"There are no problems with the current regulations," said Bryan Faehner, a spokesman with the National Parks Conservation Association. "It is there to provide the park rangers an important tool to prevent poachers from moving around national parks with impunity."
Few national parks allow hunting, and those that do lift the restrictions for the hunting season.
The Coalition of National Park Service Retirees, the Association of National Park Rangers and the Ranger Lodge of the Fraternal Order of Police also oppose the proposed changes.