The Fond du Lac Band of Lake Superior Chippewa is stepping into the legal battle surrounding the proposed PolyMet copper-nickel mine.

According to a press release from the Fond du Lac Reservation Business Committee, on Sept. 10, the Band filed a lawsuit in Minnesota federal district court against the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers.

The lawsuit is significant to the Band because the proposed mine will be located in the Ceded Territory where the Fond du Lac Band retains treaty rights to hunt, fish and gather. It is also 70 miles directly upstream...