Environmentalists are suing the Minnesota Department of Natural Resources (DNR) to ban copper mining in the watershed that flows into the Boundary Waters Canoe Area Wilderness (BWCAW).

It's the latest legal action amid the contentious push to open Minnesota to copper-nickel mining for the first time, with Chilean mining giant Antofagasta planning a large underground mine just outside the pristine Boundary Waters, near Ely.

Northeastern Minnesotans for Wilderness, a leading group in the Campaign to Save the Boundary Waters, filed its lawsuit Wednesday in Ramsey County District Court. It names the DNR and Commissioner Sarah Strommen as defendants.

The Minnesota Environmental Rights Act obligates the state to protect the Boundary Waters, according to the complaint, but the state's 1990s-era nonferrous mining rules don't adequately protect the Boundary Waters from the effects of nonferrous mining, which has never been done before in Minnesota.

The group wants a judge to order the DNR, which regulates mining, to review the nonferrous mining rules and make changes, including a ban, "to prevent a uniquely toxic and accident-prone form of mining from occurring in the Rainy River-Headwaters, waters that flow into and are in the same watershed as the BWCAW, and threaten the water and land of these unique and vital natural resources."