POWELL, Wyo. (AP) - After 30 years of renting snowmobiles to Yellowstone National Park's winter visitors, the Pahaska Tepee lodge has pulled out of the business, citing confusion over federal rules and the increased overhead those rules have created.

"It was a really hard decision," Pahaska owner Bob Coe told the Powell Tribune for Tuesday's editions. "Snowmobiles were a substantial part of who we were and of our business."

Rules published last month in the Federal Register allow up to 720 snowmobiles to enter the park, including 40 from the East Entrance. Pahaska, which has 24 snowmobiles, would have been the primary rental site for the East Entrance.

The rules also require that snowmobiles use the best available technology to reduce pollution and that a licensed guide accompany any snowmobilers inside the park - rules that vendors said have reduced the profit margin for renting the machines.

"The biggest factor driving us out is that the Park Service won't let private individuals into the park without a guide," Coe said.

Pahaska's withdrawal leaves Rimrock as the only snowmobile vendor on the East Entrance. Rimrock has 10 snowmobiles, but can rent no more than nine at a time because one must be ridden by the guide.

"The price we have to charge is a little more expensive with the guide and the special machines, but we try to make it affordable for people," said Dede Fales, co-owner of Rimrock Ranch. "We're pretty much just breaking even."

Environmentalists and tourism advocates have sparred for years over whether snowmobiles should be allowed in the park. Environmentalists say emissions from the snowmobiles pollute the park's air, and that grooming roads for the machines can affect wildlife, particularly bison.

The Wyoming Lodging and Restaurant Association sued to challenge the new rules, saying "citizens should have access to Yellowstone during its most spectacular time."

But until the rules are changed, Coe said it was unlikely he would re-enter the snowmobile market.

"We'll keep a few sleds, but sell most of them off. I just don't see us using them anymore. I don't see the Park Service changing their policies," Coe said. "If the Park Service ever changed, there's a good chance we could come back. But for right now, it's over."

Information from: The Powell Tribune, http://www.powelltribune.com