In a landmark victory for Michigan First Nations and others working to defend the Great Lakes ecosystem, the Michigan Supreme Court has rescinded a permit critical to Enbridge Inc.’s plan to replace a section of its Line 5 pipeline through under the Straits of Mackinac with a new subterranean tunnel for oil and natural gas liquids.

“Today is a reminder that when people stand together with courage and conviction, change is possible,” Bay Mills Indian Community President Whitney Gravelle told media Aug. 3. “The Straits of Mackinac are not simply a route for an oil pipeline. They are sacred waters, the heart of creation for Anishinaabe people, and a source of life for millions.”

The Bay Mills Indian Community, an Anishinaabe people whose traditional homelands and treaty-protected waters include the Straits of Mackinac, was among several groups celebrating the Michigan Supreme Court decision last week to order the Michigan Public Service Commission to redo, in its entirety, a key permit it granted in 2023 to Enbridge, the Calgary-based pipeliner that owns and operates the 73-year-old Line 5 pipeline.

The scrapped 2023 permit was an essential step in Enbridge’s longstanding quest to bore a concrete-lined tunnel deep beneath the Straits. The 6.4-kilometre tunnel would replace an equivalent section of twinned Line 5 pipeline that currently rests on the lakebed between Lakes Michigan and Huron.

The court ruling comes some 17 months after the Michigan Court of Appeals rejected a legal challenge brought against the Michigan Public Service Commission by four First Nations and three environmental groups seeking to overturn the 2023 permit.

In April, 2025, the Bay Mills Indian Community, the Little Traverse Bay Bands of Odawa Indians, the Grand Traverse Band of Ottawa and Chippewa Indians, the Nottawaseppi Huron Band of the Potawatomi, alongside Flow Water Advocates, the Environmental Law & Policy Center, and the Michigan Climate Action Network, asked the Michigan Supreme Court to overturn the lower court’s decision.

The applicants argued that in deferring to the Public Service Commission’s earlier applications of the Michigan Environmental Protection Act (MEPA) to the Line 5 tunnel proposal,  the appeals court had violated a fundamental MEPA tenet that requires courts to consider all applications of the act de novo, that is, without reference to prior ones.

The applicants also argued that the appeals court—and by extension, the commission—had violated the state’s longstanding common-law public trust doctrine.

“Consistently reaffirmed” by the Michigan Supreme Court “as a bedrock principle in Michigan law,” this doctrine “stands for a very simple premise, which is that the waters and bedlands of our lakes, our precious lakes and rivers and streams, are not for the use of private corporations or individuals, being rather held in trust for the public,” Riyaz Kanji, attorney for Flow Water Advocates, said at the media briefing.

Under the public trust doctrine, the Public Service Commission must now fully and completely consider the potential impacts of the proposed tunnel—including “whether the tunnel project will factually and proximately cause the extension of Line 5’s operational life, potentially resulting in additional environmental harm,” according to the Reporter of Decisions in a brief explaining the 6-1 Supreme Court ruling.

“The court’s decision upholds the bedrock principles of Michigan environmental law,” said Earthjustice senior attorney Adam Ratchenski during the briefing. “This decision sets forth a well-reasoned and clear framework for all Michigan agencies, one that does not allow for willful blindness or ignoring entire categories of pollution from a project.”

Describing the Supreme Court ruling as precedent-setting, Ratchenski emphasized its all-encompassing nature.

“This is not a case where an agency looked at 95% of the issues and the court said just go back and do the other 5%. The court rejected the commission’s framework of analysis and sent it back to the drawing board,” Ratchenski said.

“It said ‘go back and do it right this time’, and we’ll be fighting every step of the way to make sure that happens.”

Chad Hughes, attorney with the Environmental Law and Policy Center, said the ruling affirmed a “proper standard of review” for courts evaluating agency determinations of MEPA.

In ruling that courts must undertake “independent and searching” reviews of MEPA applications by agencies like the Public Service Commission, the Supreme Court has made the legislation itself “more forceful, more substantive, and less formalistic,” Hughes told the media briefing.

In the wake of the ruling, Ratchenski said he anticipates a new hearing before the Public Service Commission “sometime in 2027,” then “some months after that, an additional decision.”

The briefing ended with comment from Bay Mills Indian Community president Gravelle. She described the Michigan Supreme Court ruling as the lifting of a shadow, the ending of a 70-year period of silencing.

“When Line 5 was built in 1953, the voices of tribal nations and tribal consultation were not conducted,” she said. “And so for more than 70 years, we have lived under the shadow of Line 5, and every single day, we’ve carried the knowledge that one rupture could forever change the waters that define who we are.”

She added: “We cannot be Anishinaabe without the Great Lakes.”

The Supreme Court’s decision gives the community “the possibility of a future where that shadow is lifted and where the Great Lakes are no longer held hostage, because finally tribal voices are being included in the conversation,” Gravelle added.

[Disclosure: The Energy Mix Productions professional services team is currently engaged in a project on the Line 5 pipeline. No one from that team was involved in researching, writing, or editing this story.]