The close mining ties of a Washington, D.C., law firm hired to protect Minnesota against possible lawsuits related to PolyMet Mining Corp. have drawn sharp protests from a leading environmental group and some state legislators.

Crowell & Moring, which the Dayton administration retained last month, has a long history of representing the mining industry. Its clients include the National Mining Association, several coal mining and oil drilling companies, and Massey Energy, whose former CEO, Don Blankenship, was convicted this week of criminal safety violations related to the 2010 Upper Big Branch mine disaster in West Virginia.

In a sharply worded letter to Gov. Mark Dayton, an attorney for the Minnesota Center for Environmental Advocacy (MCEA) said the choice seems to “predetermine” the outcome of key decisions regarding PolyMet’s controversial proposal for a copper-nickel mine, even as the governor has repeatedly said he remains neutral and undecided.

“The decision to hire Washington, D.C., attorneys that regularly represent the mining industry raises significant questions about the state’s position on PolyMet before the state has made any decisions,” said Kathryn Hoffman, MCEA’s lead mining attorney. Hoffman also said the firm would wind up unable to represent Minnesota because its other clients would create a conflict of interest in violation of legal ethics.

State Management and Budget Commissioner Myron Frans, who is guiding the process, said the state chose the sharpest lawyers for an exceptionally good price, and said they are able to represent the state’s interests.

Frans said the firm has reviewed its potential conflicts and is able to create an ethical wall between its other clients and the state of Minnesota.

“They like to work both sides of the issue,” he said. “It’s an opportunity to get them on the public service side.”

Frans said he is writing to the MCEA and legislators who have expressed similar concerns.

Minnesota hired the firm to defend it against what many see as inevitable lawsuits whether it approves or rejects the proposed mine, a $650 million open pit and processing facility near Hoyt Lakes. An environmental review, required by law and nearly 10 years in preparation, was completed last month, and PolyMet is expected to apply early next year for the necessary permits.

While insisting that he is undecided on the PolyMet proposal, Dayton has called this one of the most important environmental decisions he will make as governor — and one that has the potential to divide the state. Proponents say the 350 jobs can help rejuvenate the economically depressed Iron Range. Environmentalists fear that a new type of mining will create unprecedented risks for water pollution.

The state has run into conflict-of-interest problems before in environmental litigation. It’s been embroiled in a 3½-year dispute with 3M Co. in one of the largest environmental lawsuits in Minnesota history. But for most of that time, the case has been mired in a side dispute over whether the state’s Washington, D.C., law firm should be disqualified because it once represented 3M.

Frans said Crowell & Moring has already taken the steps it needs to take with other clients, and that conflict of interest is not a risk.

“So far the National Mining Association has not inserted itself into the [PolyMet] process,” he said. And in the future, the law firm will avoid any work for the association that could pose a problem, he said. “We’ve got an ethical wall up,” he said.

There are, however, more subtle problems, said Richard Painter, who teaches legal and government ethics at the University of Minnesota Law School. He was hired by 3M as an expert witness in its dispute with the state.

“My gut reaction is, if your decision is to deny the permit, then mining company lawyers are not going to be your best advocates,” he said.

Painter also questioned whether Minnesota and the law firm can fully assess potential conflicts of interest before the state decides for or against PolyMet’s plan.