Stewart's bill, which is before the Natural Resources Committee awaiting a hearing, would amend the 1971 Wild Free-Roaming Wild Horses and Burros Act to allow a state or tribe to take over the animals' management from the federal Bureau of Land Management.
The number of wild horses is rising fast on drought-stricken public ranges, driving controversy as livestock and wildlife compete for forage and water.
"If we don't do something to manage these herds, it's not a good outcome," Stewart said.
A National Academy of Sciences panel last year said BLM's practice of periodic roundups makes the problem worse, and recommended much more use of birth control if the BLM doesn't want to see horses self-regulate through starvation and thirst.
In the areas where wild horses range, springs and other water sources are dominated by horses, Bates said, to the point that other wildlife suffers. "They congregate and are domineering. They preclude other animals from getting in there," he said.
Any state plan could take into account the other animals using the resource.
Utah ranchers in Iron and Beaver counties whose cattle and sheep share the range have been demanding that BLM remove horses to bring down the numbers to the agency's prescribed limits. County leaders are drumming up support for Stewart's bill and Gov. Gary Herbert endorses it, calling Stewart's bill "an important first step" toward states demonstrating to the federal government that they can handle issues.
"States are better positioned to resolve local problems than a distant federal government," Herbert said in a statement. "The state of Utah can do a better job managing the wild horses and burros within our borders than anyone else."
Wild horse advocates, meanwhile, argue that the BLM exaggerates the horse numbers and, in any case, that livestock should be booted off the public range before horses.
The BLM did not immediately respond to a request for comment about Stewart's bill, but the congressman said agency leaders are supportive.
"We've talked with the director on down. I don't want to speak for them, but they would love to have this headache taken off their plate," Stewart said. "They agree with us on the principle that the states are competent to handle" horses and burros.
Congress has slowed its activity during this election year, making quick passage unlikely. But Stewart is optimistic, citing bipartisan support from Democratic Sen. Harry Reid of Nevada, the state with more than half of the nation's wild horses.
The BLM says it spent $46 million last year warehousing 46,000 horses and 1,000 burros that it had removed from public lands but was unable to adopt out.
Another 49,000 horses and burros remain on ranges in 10 western states, which is 22,500 more than the BLM's own prescribed maximum numbers. The agency says it lacks the resources to continue stockpiling more and more animals.
The agency had planned no roundups this year, but under pressure from ranchers, county and state leaders, announced last week that it will gather 2,400 animals most of them horses through the fiscal year ending Sept. 30.
The only roundup in Utah will be in the Bible Spring Complex that straddles Iron and Beaver counties. Some 200 horses are to be removed there later this month, mostly from Utah state trust lands where the horses are not supposed to roam.
The federal act does not preclude slaughtering excess animals, but Congress forbids it each year with language in the program's appropriations bills.
Stewart's amendment would free up the states to sell horses for slaughter, if they so chose, but the congressman contends there are other good options for controlling horse populations.
He suggests the stallions could be gelded to dramatically slow population growth.
In a news release Tuesday, wild horse advocates said Stewart's bill is an attempt to bypass the congressional prohibition on selling animals for slaughter.
The American Wild Horse Preservation Campaign, a national coalition of horse advocates, also said the bill advances the agenda of anti-federal government extremists.
"Putting states and tribes in charge of managing federally protected wild horses and burros would turn back the clock four decades to a time when these animals were brutally rounded up and sold for slaughter," said Suzanne Roy, the campaign's director, according to the news release.
Stewart called the allegation that his bill furthers an anti-government agenda "ludicrous."
"This isn't a radical bill. It's not a partisan bill. We have nothing in mind but the health and preservation of the animals," he said.