AUGUSTA, Maine (AP) – The fight over who has oversight of Maine tribal waters remains contentious as the state continues its two year-old lawsuit against the federal government.

Lawyers from each side are duking it out in lengthy court filings that hit on one central issue – whether water is clean enough for individual tribal members to fish for themselves within their reservations.

The Environmental Protection Agency filed an Aug. 4 brief accusing the state of trying “back door” legal maneuvers to get the courts to overturn an EPA decision calling for higher water quality standards in Indian waters in Maine.

Maine Democratic Attorney General Janet Mills has argued Maine’s water standards are some of the most stringent in the nation, and says the EPA is overstepping its boundaries.

The controversy dates back to the wording of 18th century treaties and long-standing tribal concerns about land transactions with Maine. In 1980, the state government formally struck a deal settling Native Americans’ claim to nearly two-thirds of Maine’s lands.

That 1980 decision made Maine’s relationship with tribes unlike most other states in the nation.

Maine argues that because of the 1980 law and a 2007 federal appeals court ruling, it has environmental regulatory authority over all land in the state, including tribal lands. The state wants the courts to review the EPA’s decision now under federal laws like the Clean Water Act.

The state says Maine’s water quality standards apply the same statewide, even in tribal waters. It adds that Maine law only exempts Penobscot Nation and Passamaquoddy Tribe sustenance fishers from hunting rules like bag limits.

But the EPA says that the state’s water quality standards for toxic pollutants aren’t stringent enough. It contends Maine’s tribal sustenance fishers eat more fish than Maine’s general population.

The agency claims the court can only review the EPA’s decision after it officially puts forth the new rules.

None of the four federally recognized tribes in Maine are taking part in this lawsuit.

But the Penobscot Nation teamed up with the federal government on another lawsuit that poses a similarly thorny question: whether the Penobscot Nation’s reservation includes just the islands of the main stem of the Penobscot River, or the waters as well.

Last December, U.S. District Court Judge George Z. Singal ruled that the reservation doesn’t include the waters. He said the tribe could not charge people with violations of fishing regulations or water quality rules.

The ruling also granted the Penobscot Nation the right to take fish for individual sustenance in that part of the river.

Both sides have told the court they will appeal the decision, though oral arguments are not scheduled.

A message was left for Penobscot Nation Chief Kirk Francis but he was not available to comment. The tribe’s general counsel, Mark Chavaree, did not respond to multiple requests for comment.