ROCKY MOUNTAIN NATIONAL PARK, Colo. - Guns tend to bring out a black-or-white, yes-or-no stridency in American policy debate. Guns are bad. Guns are good. Guns are dangerous. Guns keep you safe.

The National Parks evoke equally deep emotional feelings - about place. Setting aside specific spots for the celebration of nature, or history, or spirituality, is an old tradition - as old as the Second Amendment.

Now those emotions are colliding.

A new law passed by Congress and signed by President Obama last week will allow guns in the parks and national wildlife refuges. Attached as an amendment to an overhaul of credit card rules, the law will take effect next year. Fine-print rules, allowing both concealed and openly carried weapons, are now being written at the Department of the Interior, which runs the parks system.

How gun owners and weekend warrior hikers can find accommodation on this new trail is only part of the story. Parks officials are also scratching their heads about how the new rules will affect enforcement of laws on things like gun permits, which vary widely and will still hold sway even on federal park lands, and wildlife poaching. Some people believe that the change will be immense, others that it will not be noticeable at all.

One park visitor here was not sure what to think.

"Gun rights are gun rights, but do you need them in a location like this?" said Russell Lahrmann, a dentist from Industry, Tex., near Houston, who was hiking on Tuesday on a trail around Bear Lake with his wife, Lisa, and their 8-year-old son, Luke.

Mr. Lahrmann said he owns guns - they are just part of life in Texas. But in coming here, he said, glancing around at the blue lake with the towering mountains behind it, it would not occur to him to want his weapons.

"It'd be like carrying around a bowling ball - you could do it, but why would you?" he added. "I don't feel unsafe here."

Park rangers and volunteers said they were not sure whether gun possession in the park would increase or not when the new law takes effect, partly because they have no idea how many visitors are illegally carrying concealed weapons now. Hardly anyone is ever caught, though current law requires owners to lock or store their guns in a trunk or glove box while in the parks.

"If a person is going to bring a weapon in here, they'll do it whether there's a law or not," said Major Sansam, a seasonal volunteer at Rocky Mountain National Park, the seventh-most popular in the system, with about 2.8 million visits last year.

Law enforcement of illegal hunting is another area of some confusion. Under current law, carrying or transporting a loaded weapon in plain sight is considered probable cause to stop a visitor as a possible poacher. The elk population, in particular, is huge at Rocky Mountain. After the new law, hunting will still be illegal, which means rangers will have to catch people in the act.

Scot McElveen, president of the Association of National Park Rangers, said an officer would have to "see somebody shoot at wildlife or catch them standing over the carcass."

The chief ranger at Rocky Mountain, Mark Magnuson, said his officers were already taught to act as though any visitor could be armed, so the new rules might not mean much in terms of training or preparation. Still, he said, it will probably be in a ranger's mind when he or she is called to respond to rowdy or drunken campers at night, or meets a hiker alone on a backcountry trail.

"People don't leave their problems at home when they go to recreate," Mr. Magnuson said.

An equally thorny question involves state jurisdiction. Under the federal law, existing state law will determine how the regulations work in each park. State laws can differ, so in parks that straddle state lines - like Yellowstone, spread across Wyoming, Idaho and Montana, and Death Valley, in California and Nevada - different laws may apply in different sections.

"What happens if there is a pursuit of someone with a firearm in a National Park and they cross state lines?" said Bryan Faehner, an associate director for the National Parks Conservation Association, a nonprofit group. "How are they going to know what state they are in?"

Colorado, like other states, also recognizes concealed weapons permits from some states but not others. A permit issued in Texas or Pennsylvania is valid in Colorado, for example, and would thus eventually be recognized in Rocky Mountain. But a permit holder from California or New York would still have to leave his or her guns locked away, because permits from those states are not recognized here.

Some visitors said the feel of Rocky Mountain, and the national parks in general, could change, and not for the better, if the sight of a gun on a backpacker's hip becomes common.

"I like the idea that there are places that are weapon-free," said Denise Larson, a school language instruction aide from Topeka, Kan., who was visiting the park with her husband, Will. "This should be one of them."

Other visitors said that rules should be uniform and that if a person had a valid legal permit, federal park land should be no different from any other place.

"I don't see any problem," said Ken Pike, a retired automobile dealership worker from Garland, Tex., near Dallas. Mr. Pike said he owns guns, but did not have a permit to carry a concealed weapon. "If I did, I'd carry it anywhere I went, as long as it was legal," he said.

Dan Frosch contributed reporting from Denver.