Several environmental groups are challenging Minnesota's plan for reducing haze in national parks and wilderness areas.
The lawsuit was filed in U.S. Court of Appeals, Eighth Circuit, in St. Louis over Minnesota's plan to reduce haze in places like the Boundary Waters Wilderness and Voyageurs National Park.
The federal haze rule says power plants and other industries that pollute the air in those places and similar areas must reduce pollution by installing best available control technologies.
The Minnesota plan offers more flexibility for power plants, allowing them to follow a different program, the cross-state air pollution rule. The state says that will accomplish just as much pollution reduction as mandating specific technologies.
However, several environmental groups disagree. Christine Goepfert from the National Parks Conservation Association says under the state's approach, power plants can trade with each other for pollution allowances, leaving no guarantee of improvement.
"Essentially they're getting away with not putting in better controls so we'll actually see some reductions in pollution," Goepfert said.
The Minnesota Pollution Control agency has said the pollution trading program will clean up the air just as well as the haze rule would, but did not immediately respond to a request for comment on the lawsuit.