The state of Minnesota is bailing on its effort to devise a plan to protect wild rice from pollution that comes from taconite mines and wastewater treatment plants, ending a nearly 10-year political and legal fight over Minnesota's official state grain.

"We've heard many, many voices … and the message is clear," says John Linc Stine, commissioner of the Minnesota Pollution Control Agency. He said that the scientific research that the state has conducted in recent years is accurate and well founded, but when it comes to applying it through regulation "we still have more work to do."

The MPCA plans to withdraw from the rule-making process, and will now turn to the Legislature for guidance on how to move forward.

The proposed rule, which has sparked fierce political fights and multiple lawsuits since the state began writing it in 2010, was designed to regulate sulfate, a mineral salt that damages wild rice. It is produced by taconite mines, wastewater treatment plants and other industries. While the state's rule is specific to wild rice, sulfate also plays a part in converting mercury into a form that is taken up by fish, creating significant health risks for pregnant women and children.

The final proposal was opposed by Minnesota's Indian tribes, environmental groups, industry and wastewater treatment operators. But they opposed it for different reasons.

Environmentalists and the tribes said the state's existing sulfate standard of 10 parts per million, which has been in place since the 1970s, is enough to protect wild rice if the standard is enforced. With few exceptions, however, the state has not done so.

Industry representatives said the state's new rule would be prohibitively expensive and unworkable: The highly complicated plan would use a chemical formula to set sulfate limits on discharges upstream of each of 1,300 individual lakes or rivers where wild rice grows.

In January, LauraSue Schlatter, the administrative law judge charged with deciding whether the proposed rule is reasonable, agreed with both arguments. She reimposed the MPCA's original standard of 10 parts per million, saying that the state's decision to repeal it was a violation of the federal Clean Water Act. She also concluded that while the formula approach had scientific validity, the state could not effectively implement it without first conducting years of study on the 1,300 wild rice waters. It was unconstitutionally "void for vagueness," she said.

More recently, Republican lawmakers proposed a bill that would require the MPCA to start over, while also forbidding the agency from enforcing the current standard.

An agency spokesperson said officials are still discussing how the current standard will be enforced.