Attorneys general from three states, including Minnesota, have filed briefs supporting an argument made by the Michigan Attorney General in a lawsuit filed to shut down Enbridge’s Line 5 oil pipeline under the Straits of Mackinac.

The amicus briefs, or friend-of-the-court briefs, filed by the attorneys general of Minnesota, Wisconsin and California back Michigan Attorney General Dana Nessel's argument that the land under a lake is within state, not federal, jurisdiction.

Nessel filed a lawsuit filed in June arguing Enbridge violated its 1953 easement through the strait, the public trust doctrine, and the Michigan Environmental Protection Act as “it is likely to cause pollution, impairment and destruction of water and other natural resources.” Nessel is also seeking an order from a judge that would shut down and decommission the pipeline.

In a statement, Nessel said she was “grateful” to have the support of three other state attorneys general.

“It is rare to have the amicus support of other state attorneys general in a state case but the attorneys general for two of our fellow Great Lakes states and the state with one of the longest coastlines in the country clearly recognize the severity and the magnitude of this issue and the important role states play in protecting the public trust,” Nessel said.

In an emailed statement, Minnesota Attorney General Keith Ellison cited a U.S. Supreme Court decision from more than 125 years ago that affirmed a state holds the land underneath its waters in the public trust.

“This public trust doctrine isn’t new: it’s rooted in Roman law and English common law. I joined the attorneys general of Wisconsin and California in supporting the state of Michigan in protecting its right to control its underwater land against the federal government’s attempt to preempt it,” Ellison said. “The people of Michigan, who share the Great Lakes with us, have as much of a right to control their underwater land as the people of Minnesota do. By supporting Michigan, I’m protecting Minnesotans.”

Xavier Becerra, Attorney General of California, and Joshua Kaul, Attorney General of Wisconsin, joined Ellison on the brief.

Responding to the brief, Enbridge spokesperson Juli Kellner stressed Line 5 has been operating safely in the strait since 1953.

“There is no change in the operating condition of the pipeline or change in law to support the Attorney General’s position,” Kellner said.

Line 5 splits into two pipes as it travels the lake bottom for 4.5 miles across the strait, where Lake Michigan and Huron meet, and runs parallel to the Mackinac Bridge.

The 640-mile pipeline carries up to 540,000 barrels of oil per day from Superior to Sarnia, Ontario by way of Michigan’s Upper and Lower peninsulas.

While an oil spill has never been recorded in the strait, environmentalists fear the impact of a potential spill’s pollution would be catastrophic to the Great Lakes.

In April, an anchor struck and dented the pipeline, and in August, Enbridge reported more than 80 feet of Line 5 was unsupported as erosion had washed away the lake bottom below it.

Enbridge said it plans to keep Line 5 by constructing a tunnel under the strait and routing the routing the pipe through it.

“Our focus is on the work currently going on in the Straits of Mackinac. We are moving forward with our rock and soil sampling, which is part of our $40 million investment in pre-construction work on the tunnel,” Kellner said. “We believe this allows us to stay on schedule and ensures the earliest possible date for completing the project.”

In Minnesota, Enbridge continues to push for the construction of a new Line 3 oil pipeline, but the project faces numerous legal and regulatory hurdles. The pipeline would replace Enbridge's existing 50-year-old Line 3, but follow a new route through much of the state, and carry 760,000 barrels of oil per day from Alberta to the Enbridge terminal in Superior.

State Rep. Dan Fabian, R-Roseau, said he was frustrated by the attorney general's support for the Michigan lawsuit and worried that sentiment could carry over to future decisions or litigation surrounding the Line 3 oil pipeline.

“Here we go again, not necessarily with Attorney General Ellison, but more of what I would call obstruction on these infrastructure projects, these pipeline projects that need to get done,” Fabian said. "I wish he just would've stayed out of it. I think it just takes away any appearance of impartiality moving forward."

Forum News Service reporter Dana Ferguson contributed to this report.