The nation's largest gun manufacturer has begun instructing distributors not to sell its firearms at gun shows, apparently the first policy of its kind, the Denver Post reported today.

In contracts with distributors this year, Sturm, Ruger & Co. states that its shotguns, rifles and handguns should be supplied only "to federally licensed firearms dealers selling exclusively from their regular place of business," the newspaper said.

Millions of guns are sold or traded every year at an estimated 4,400 gun shows nationwide. Federally licensed gun dealers must conduct background checks on gun-show customers, but unlicensed private dealers are not required to conduct the checks.

"This is a new policy that no other manufacturer has made. I think what they're doing is remarkable," said Tony DiChario, a Ruger distributor in Rochester, N.Y.

In a written notice, his company, AmChar Wholesale, has asked about 5,000 retailers to adhere to the new policy.

"Please do not display or sell any Ruger firearms at any gun shows. Ruger firearms must only be sold from licensed retail dealer establishments," the notice states.

Unregulated sales at gun shows became a target of criticism after weapons sold without background checks at the shows were used in the Columbine High School massacre. Fifteen people, including the two gunmen, died in the attack last spring.

But Colorado's largest firearms dealer questioned why customers who pass background checks should be treated differently at gun shows than at stores.

"I think it's absolutely ludicrous," said Dave Anver, owner of Dave's Guns in the Denver suburb of Aurora. "We're talking about federally licensed entities that do background checks."

Sturm, Ruger, based in Fairfield, Conn., has made and sold more than 13 million guns since it was founded 50 years ago. It ranked as the top gun manufacturer in the United States last year.

Company officials declined to comment on the reasons for the new policy.

Sturm, Ruger remains a defendant in lawsuits filed by 28 cities and counties seeking to recover the costs of gun-related violence, according to the Post.

Other gunmakers, including California-based Davis Industries, have taken steps to limit their liability. Davis, a company that specializes in cheap handguns, filed for bankruptcy protection in May. And Colt's Manufacturing Co. announced last fall that it was curtailing its production of handguns.