In a victory for gun-rights advocates, the federal government is preparing to relax a decades-old ban on bringing loaded firearms into national parks.

Interior Secretary Dirk Kempthorne said Friday that his department would suggest new regulations by the end of April that could bring federal rules into line with state laws concerning guns in parks and public lands. His announcement came in a letter to Sen. Michael D. Crapo (R-Idaho), one of 50 senators who have written to him about the issue. Senators from both parties have backed a drive to repeal the ban, which has been in place in some parks for at least 100 years.

The proposed rule change would let visitors carry loaded weapons into national parks in states with few gun restrictions, such as Montana.

California is not one of those states. Its law prohibits loaded guns in state parks unless they are locked inside a car trunk or are similarly inaccessible. "It's a place of refuge, not a place for hunting, and it's patrolled by state park rangers who are there to protect visitors," California State Parks spokesman Roy Stearns said.

Gun rights advocates, notably the National Rifle Assn., have said the ban infringes on their 2nd Amendment rights to bear arms and their ability to defend themselves from predators, both human and animal.

"If you're hiking in the backcountry and there is a problem with a criminal or an aggressive animal, there's no 911 box where you can call police and have a 60-second response time," said Gary S. Marbut, president of the Montana Shooting Sports Assn.

Kempthorne's decision to review the ban was hailed by the NRA. "This is an important step in the right direction," said the organization's chief lobbyist, Chris W. Cox.

On the other hand, the National Parks Conservation Assn. called Kempthorne's action "alarming." Thomas C. Kiernan, the group's president, said loosening the ban would be "a blow to the national parks and the 300 million visitors who enjoy them every year."

His view is echoed by gun-control advocates and some rangers who say that permitting firearms would be dangerous for visitors and wildlife and would alter the national park experience.

"Parks have long been sanctuaries for both animals and people," said Charles R. "Butch" Farabee, a former acting superintendent at Montana's Glacier National Park who is retired. "There need to be places in this country where people can feel secure without guns and know that the guy in the campground across the way does not have one."

Although a federal rule change would not directly affect California, George Durkee, a board member of the U.S. Park Rangers Lodge of the Fraternal Order of Police who works at Sequoia and Kings Canyon national parks east of Fresno, worries about gun owners from other states: "Somebody who says, 'Oh, well, I can now carry a gun in national parks,' and doesn't read the fine print will just figure he can carry one in Yosemite."

The federal government would not cede authority over firearms in national parks to the states, said Interior Department spokesman Chris Paolino, but would like to reflect the policies of host states. Paolino said the department would also take into consideration the ban on firearms in federal buildings.

Weapons originally were prohibited in national parks to prevent "opportunistic poaching" of wildlife, said Frank Buono, a former assistant superintendent of Joshua Tree National Park, east of Palm Springs.

A 1908 Yellowstone National Park regulation, for example, required that visitors "having firearms, traps, nets, seines or explosives" surrender the weapons at the entrance unless they received written permission from the park superintendent. A similar policy was in effect at most parks for decades. Then the Reagan administration in 1983 required that visitors unload and store their firearms before entering most parks.

Supporters of the repeal effort note that state gun laws apply to federal land managed by the Forest Service and the Bureau of Land Management, and they think that should be the case in national parks and wildlife refuges as well.

Half of the Senate seems to agree. Nine Democrats and 41 Republicans have signed letters to Kempthorne calling on him to lift the gun ban. "We do not believe that allowing law-abiding citizens to transport and carry firearms -- rather than forcing them to disassemble or store them in their trunks -- will increase the chances that they will be tempted to violate prohibitions on discharge," one group wrote.

In campaigning to repeal the ban, the NRA hoped to add to a string of recent victories that included blocking an effort in Congress to give local law enforcement officials access to federal gun purchase data and a move in Virginia to require background checks for buyers at gun shows.

In a measure of the bipartisan support for relaxing gun laws, a majority of Congress -- 55 senators and 250 House members -- recently urged the Supreme Court to strike down the District of Columbia's handgun ban, one of the nation's strictest.

Advocates of allowing loaded guns in national parks believe it is foremost an issue of ending what they see as an unconstitutional infringement on their right to bear arms. But they also contend that park visitors are "increasingly vulnerable" to violent crime.

"While park rangers now use bulletproof vests and automatic weapons to enforce the law, regular Americans in states where conceal-and-carry law exists are denied the opportunity for self-defense," Sen. Tom Coburn (R-Okla.) said in "talking points" distributed by his office.

The National Park Service says there were 116,588 reported offenses in national parks in 2006, the most recent year for which data are available, including 11 killings, 35 rapes or attempted rapes, 61 robberies, 16 kidnappings and 261 aggravated assaults.

Supporters also think gun owners should be able to protect themselves against dangerous animals, dismissing arguments that firearms would ruin the park experience. "An attack, whether by an animal or a criminal, would degrade the experience of park visitors more," NRA spokesman Andrew Arulanandam said.

The park service said there were four bear attacks last year: two in Yellowstone, one in Sequoia and one in Grand Teton. There were none in 2006.

Officials at Glacier -- which recorded 10 deaths from grizzly bear attacks between 1967 and 1998 -- said the last attack was in 2005, when two hikers were mauled.

One of the victims, Johan Otter, an Escondido man who, with his daughter, was seriously injured, said the idea that a gun could have stopped the 400-pound bear that charged him is naive.

"We only had, like, half a second between seeing the bear and the impact," Otter said. "Most likely, if you shoot, you're going to hurt the animal. It's just going to get even more mad at you. The minute they're on top of you, there's no way you can pull a trigger."

Organizations that represent current and retired park workers oppose a repeal, saying it would endanger visitors, rangers and wildlife, and change the parks' character.

Bill Wade, executive council chairman of the Coalition of National Park Service Retirees, said people could be discouraged from visiting certain parks, such as Shenandoah National Park in Virginia, where he served as superintendent. "How many of you would want to go out there if you knew that people were running up and down the Appalachian Trail with guns?"

richard.simon@latimes.com

judy.pasternak@latimes.com