The federal government has ordered Maine to tighten its water quality standards for rivers and lakes on tribal lands to ensure fish taken there are safe to eat in large quantities.

Tribal leaders hailed the move as a historic assertion of federal oversight of Maine’s relationship with federally recognized tribes here.

The U.S. Environmental Protection Agency ruled Monday that clean water standards proposed by the state Department of Environmental Protection are inadequate to protect sustenance fishermen – those who fish as a primary means of feeding their families – on the reservations from certain toxins, because they eat much greater volumes of fish than the average Mainer. The EPA ruling does not suggest that eating fish from the state’s waters is unsafe for most Mainers.

After closely consulting with the U.S. Department of Interior’s Bureau of Indian Affairs, EPA also ruled that Maine must protect sustenance fishing on Indian lands because it is a “critical element of tribal cultural survival.” This in turn is a “clear purpose” of the Maine Indian claims settlement acts, the historic 1980 laws whereby the state and tribes negotiated a compromise to avoid a legal battle over the tribes’ claim to more than half of Maine’s territory.

In a Feb. 2 letter to Maine DEP commissioner Patricia Aho, the EPA ordered the state to come up with stricter standards for mercury, arsenic, acrolein and phenol within 90 days, or else the agency will impose standards. States are required to set water quality standards under the federal Clean Water Act, and submit them for EPA review and approval.

“It’s a truly historic decision,” said the chief of the Penobscot Nation, Kirk Francis. “We’re elated that the federal government is saying (to Maine): ‘You’re wrong. These are federally recognized tribes with federal protections and rights, and you can’t just point to some legal language and say it means you can take those things away.’ ”

The ruling appears to put the state and federal governments on a collision course over Maine’s jurisdiction in environmental matters on Indian lands. For decades, the Maine Attorney General’s Office has maintained that 1980 settlement acts give the state full jurisdiction over environmental regulation on tribal lands. (In other states, tribal lands are generally under federal jurisdiction.)

Although the EPA acknowledged that a federal appeals court in 2007 ruled Maine does have jurisdiction in environmental matters, it “also finds that this authority is not unconstrained.”

“EPA found the state must protect the tribes’ sustenance fishing practices as a designated use of tribal waters consistent of the settlement acts to set aside lands and waters to support tribal sustenance culture,” the agency said in a written statement.

Attorney General Janet Mills’ office disagreed. In a written statement, Mills’ spokesman Timothy Feeley said federal courts had “fully resolved” that Maine has “full jurisdiction to enforce environmental laws and standards” throughout the state.

“It is unclear, as a practical and legal matter, what the effect of the EPA’s unprecedented action will be,” Feeley continued. He said the state is considering whether to file a court appeal challenging the imposition of “a possible double standard for Maine waters.”

Francis said he was disappointed that EPA accepted Maine’s authority to set environmental standards, but he was “elated” that the federal government was taking up its role as trustee to the tribes.

“They’re saying that not only do we have a right to fish, we have the right to take fish that will not threaten our health, and that they as trustee will be responsible for that,” Francis said. “Maine has allowed industry to use the (Penobscot) river as a toxic waste dump … It has always aligned itself with polluters.”

Officials at the Passamaquoddy tribe and the state DEP did not respond to interview requests. The decision also affects the lands of two other federally recognized tribes, the Aroostook Band of Micmacs and the Houlton Band of Maliseets.

The EPA argues that Maine erred in setting its standards for protecting human health based on the results of a statewide fish consumption survey that assumed a person ate an average of 32.4 grams of fish a day. The EPA found that peer-reviewed studies indicate “historic sustenance fish consumption rates among the tribes in Maine of between 286 to 514 grams per day,” the agency’s statement said. It has ordered Maine to recalculate its standards based on this new criteria.

The agency did approve most of the state’s other proposed water standards dealing with the health of aquatic creatures rather than humans.

Control over tribal fishing rights in Maine – both freshwater and salt – has become a hotly contested issue. The Penobscot Nation has sued Maine over its contention that the tribe’s sustenance fishing rights are limited to bodies of water on its small island reservations, not in the Penobscot River that surrounds them. The Passamaquoddy argue they did not give up their traditional saltwater fishing rights under the 1980 settlement acts, while the state maintains they did.