The Michigan Supreme Court has ordered state regulators to reassess Enbridge's proposed Line 5 tunnel beneath the Straits of Mackinac, ruling that the state Public Service Commission failed to fully evaluate the project's environmental impacts before approving it.
In a sweeping decision Friday, the court vacated a Michigan Public Service Commission order authorizing the project, which would encase a petroleum pipeline in a tunnel under the Straits, and sent the case back to the commission for further review under the Michigan Environmental Protection Act.
In a 6-1 decision, the majority said the commission should have considered whether building the tunnel would effectively extend the life of the Line 5 pipeline and, in turn, lead to additional environmental harm. The court also found fault with the commission's analysis of alternatives to the project and said regulators failed to consider potential impacts on public trust resources protected under Michigan law.
"The PSC erred," the court wrote, by failing to consider whether the tunnel project would "factually and proximately cause the extension of Line 5's operational life, potentially resulting in additional environmental harm."
The court also laid out a broader legal standard holding that courts reviewing agency decisions under the Michigan Environmental Protection Act must independently evaluate whether a project complies with the law, rather than deferring to an agency's conclusions.
Opponents of the pipeline tunnel cheered the decision. "Today is a reminder that when people stand together with courage and conviction, change is possible," said Bay Mills Indian Community President Whitney Gravelle.
"For years, Tribal Nations, communities, and thousands of people across the country have raised their voices to protect the Great Lakes. This decision gives us another opportunity to honor our treaty rights, protect our waters, and consider the generations who will inherit this place," Gravelle said.
The decision reverses a ruling by the Michigan Court of Appeals, which had upheld the Public Service Commission's analysis using a more deferential standard of review.
Justice Brian Zahra dissented, arguing the majority improperly expanded the scope of the environmental review by requiring regulators to consider impacts tied to the continued operation of Line 5 itself, rather than just the tunnel replacement project.
The dispute centers on Enbridge's proposal to place a roughly four-mile section of the Line 5 oil and natural gas liquids pipeline inside a tunnel drilled through bedrock beneath the Straits of Mackinac.
Supporters argue the tunnel would reduce the risk of an oil spill from the existing pipeline, which now rests on the lakebed. Enbridge has said it would make an already-safe pipeline safer.
Rather than deciding whether the tunnel should ultimately be approved, the Supreme Court directed the Public Service Commission to revisit its environmental review using the standards laid out in Friday's opinion.
The ruling does not resolve the project's broader permitting process. The tunnel still requires additional state and federal approvals before construction can begin.
Editor’s note: Enbridge is among Michigan Public’s corporate sponsors.
