WASHINGTON — A federal judge on Monday threw out plans to allow more than 500 snowmobiles a day into Yellowstone National Park, saying that many snowmobiles would increase air pollution, disturb wildlife and cause too much noise in the nation's first national park.

The National Park Service's Winter Use Plan would have allowed 540 snowmobiles to go through Yellowstone and Grand Teton national parks and along the John D. Rockefeller Jr. Memorial Parkway every day, starting this winter.

"According to NPS's own data, the (plan) will increase air pollution, exceed the use levels recommended by NPS biologists to protect wildlife, and cause major adverse impacts to the natural soundscape in Yellowstone," U.S. District Judge Emmet Sullivan said in an order Monday.

Conservationists sued the National Parks Service to stop the plan. They want snowmobiling eliminated in the park, or at least reduced.

Park officials said they averaged about 290 snowmobiles a day in 2006, the most recent number available. Conservationists argued that allowing 540 snowmobiles, a cap higher than that average, would not help solve the park's problems.

"This ruling will restore the quiet and the clean air in Yellowstone for everyone to enjoy," said Amy McNamara, director of the Greater Yellowstone Coalition national parks program.

Added Kristen Brengel, director of the Wilderness Society: "The park deserves to be protected from noise, harm to wildlife and poor air quality."

The judge said letting in the proposed number of snowmobiles "elevates use over conservation of park resources and values." The National Park Service "fails to articulate why the plan's 'major adverse impacts' are 'necessary and appropriate to fulfill the purposes of the park,"' Sullivan said in his order.

The National Park Service must redo the plan, Sullivan said.

In Cheyenne, Wyoming Republican Sens. Mike Enzi and John Barrasso denounced the ruling.

"National parks are for the benefit and enjoyment of the people, and judges and lawyers seem to forget or purposely discount that sometimes. That's sad," Enzi said.

In the late 1990s, as many as 1,400 snowmobiles a day visited Yellowstone, contributing noise and air pollution that critics said was inappropriate for the country's first national park.