MONTPELIER, Vt. – The National Wildlife Federation, the Maine Wolf Coalition, Maine Audubon and two other environmental groups went to court Thursday to try to force the federal government to revive plans to restore wolves to the Northeast.

The lawsuit, filed in U.S. District Court in Burlington, charges that the Interior Department violated the Endangered Species Act last spring when it changed the classification of wolves in the continental United States from endangered, the most imperiled, to threatened.

The move by the U.S. Fish and Wildlife Service came after programs in the Rocky Mountains and upper Great Lakes states helped restore wolf populations there. Even though wolves used to live in the Northeast, no such program was implemented for the region.

“Although the thriving wolf populations in the Great Lakes and Northern Rockies are indeed wildlife success stories, they cannot be used as an excuse for abandoning the goal of wolf recovery in the Northeast,” said Eric Palola, director of National Wildlife Federation’s Montpelier office.

On April 1, the Fish and Wildlife Service reclassified most wolf populations in the United States from endangered to threatened. The move came after what officials felt was a successful reintroduction program in Yellowstone National Park. Wolves naturally repopulated parts of the upper Great Lakes from previously existing populations in Minnesota.

Federal officials have said the goal of the Endangered Species Act, the creation of a self-sustaining wolf population in the wild, has been met.

Wolves used to roam across much of North America, but they were pushed out of the Northeast in the late 1800s. Now there are no known wolf populations living in the Northeast, although there are wolves living in eastern Canada near the U.S. border, and individual wolves have been found in Maine.

There are tens of thousands of acres of suitable wolf habitat in areas of Maine, New Hampshire and the Adirondack Mountains of New York as well as corridors through Vermont.

“The Fish and Wildlife Service has an obligation under the [Endangered Species Act] to recover wolves in a significant portion of their historic range, and this includes the forests of the Northeast states,” said John Kostyack, an attorney for the Wildlife Federation in Washington.

Even before the rule change, wolf restoration plans for the Northeast weren’t far advanced. The goal to reintroduce wolves was met with fierce opposition by some people who feared the effect on wildlife and farm animals.

Joining the National Wildlife Federation, the Maine Wolf Coalition and Maine Audubon in the suit filed Thursday are the Vermont Natural Resources Council and Environmental Advocates of New York.