MINNEAPOLIS (AP) — An administrative law judge has rejected an attempt by regulators to change Minnesota’s water quality standard for protecting wild rice, saying the proposal violates federal and state law and puts an unfair burden on Native Americans who harvest wild rice for food.

In a report released Thursday, Administrative Law Judge LauraSue Schlatter said the Minnesota Pollution Control Agency failed to justify changing the state’s current standard, which limits discharges of sulfates into waters where wild rice grows to 10 milligrams per liter. The agency proposed to replace the flat limit with a complex formula tailored to the chemistry of specific lakes and streams that would allow higher sulfate discharges in many cases. The proposal also included a list of 1,300 waters where the new standard would apply.

The MPCA’s proposal upset all sides in the long-running debate — environmentalists and the state’s Ojibwe tribes on one hand, and mining companies and wastewater treatment plant operators on the other. The environmental groups and tribes said the current standard would provide better protection for wild rice stands, while the industrial dischargers wanted the old standard dropped. Both sides were sharply critical of the science behind the proposed new standard.

“This is an enormous victory,” said Paula Maccabee, an attorney for WaterLegacy, a group that’s been fighting to preserve the existing standard. “It’s not just a victory for the communities that care about wild rice and water quality and Native American rights. It’s a victory for the rule of law.”

Minnesota’s Ojibwe tribes consider wild rice to be a sacred and important food source that’s critical to their cultural identity. The tribes also argued that higher sulfate levels could translate into higher mercury levels in the fish they eat.

Minnesota adopted the flat 10 milligram standard in 1973 but it went largely unenforced until recently when the debate heated up over mining in northern Minnesota. Courts rejected ensuing efforts by industry to strike down the limit. The 2011 Legislature then approved $1.5 million to study whether the old standard, based on research from the 1930s and 1940s, needed updating, and ordered the MPCA to revise the standard accordingly.

The research ordered in 2011 confirmed that sulfates are harmful to wild rice, and found that it’s because they get converted to by bacteria to sulfides in sediments where the plants grow. But it also found that the harm depends on the interplay of sulfides with iron and organic carbon in the sediments. That led the MPCA to develop the proposed formula, which the agency called an innovative and site-specific approach when it released the plan last August.

The agency’s next move isn’t clear.

“We will need to read and evaluate what the ruling says before offering any public comment,” the MPCA said in a statement, adding that it doesn’t have a timeline yet for when it will give a more detailed response.

Chief Administrative Law Judge Tammy Pust concurred with Schlatter’s findings. If the agency chooses not to correct the defects in its proposal, she wrote, it must submit the proposal to a panel of top lawmakers called the Legislative Coordinating Commission and to key legislative committees.

However, it wasn’t immediately clear if those bodies have the authority to implement the proposed standard, or the will given the broad opposition. Schlatter cited several instances in her 80-page report where the proposal would violate federal law. Republicans have an 8-4 majority on the LCC. And a key Democrat on the panel, Senate Minority Leader Tom Bakk, a mining supporter from the Iron Range, has fought to weaken the existing standard.

Another opponent of the existing standard welcomed Schlatter’s report.

“The MPCA’s proposal lacked the sound scientific support that should be the basis for any changes, created uncertainty for permit-holders throughout the state, and would have been an unworkable barrier to job creation and the very existence of mining in Minnesota,” said Rep. Dale Lueck, vice chairman of the House mining subcommittee.