Michigan environmental regulators are reviewing permits they recently granted for the Line 5 tunnel project, in light of a recent Michigan Supreme Court decision that raised the bar for environmental reviews.

Governor Gretchen Whitmer and Phil Roos, director of the Michigan Department of Environment, Great Lakes and Energy (EGLE), announced the development Wednesday in a press release.

Calling the Line 5 pipeline “a ticking time bomb in the heart of the Great Lakes,” Whitmer also wrote a letter Wednesday urging [pdf] outgoing Enbridge CEO Gregory Ebel to shut it down “within months.”

Line 5 is part of a broader cross-border energy network and carries crude/energy supplies from Western Canada through the U.S. Great Lakes region to refineries in Ontario and Quebec. The permits now in question are related to Calgary-based Enbridge’s plan to replace the section of Line 5 that crosses the Straits of Mackinac, with a new pipeline housed inside a concrete-lined tunnel beneath the lakebed.

“The Michigan Supreme Court chas made clear that the state must more thoroughly scrutinize the environmental consequences of the proposed tunnel and the alternatives to it,” Whitmer said in a statement. “At the same time, Enbridge needs to stop asking Michigan to wait for a tunnel that could be a decade or longer away and start pursuing alternatives now that can get oil out of the Straits within months.”

Environmentalists and Indigenous tribes who oppose the pipeline celebrated the renewed permit scrutiny and shutdown push as a win for the Great Lakes, while unions and business groups that support the tunnel called it “a slap in the face.”

Four Tribal Nations in Michigan are petitioning state regulators to toss the permits, stating in a press release emailed to The Energy Mix on Thursday that the Line 5 tunnel project “will irreversibly destroy tribal cultural resources including burials, tribal lifeways, and the Straits of Mackinac, a sacred space for the Anishinaabe.”

“The Department acknowledges this destruction and highlights that the impacts to these irreplaceable cultural resources ‘exceeds that of any other that EGLE has reviewed,'” said Native American Rights Fund (NARF) Managing Attorney David Gover. “We look forward to judicial review of this legally deficient permit.”

On Monday, around 1,000 people from 12 Anishinaabe Tribal Nations in Michigan walked across the Mackinac Bridge spanning the Straits of Mackinac to demonstrate opposition to the Line 5 tunnel. On Thursday afternoon, environmental groups filed their own challenge to the same permits.

Responding to Whitmer’s Wednesday announcement, Enbridge spokesperson Ryan Duffy lamented the additional delay for a project originally pitched in 2018 with a targeted completion date of 2024.

“We continue to stand ready to meet with the Governor to look at ways that protect Michigan’s natural resources while ensuring the continued safe operation of critical energy infrastructure,” Duffy said.

For years, Enbridge has defied Michigan state’s orders to shut down its 73-year-old pipeline in the Straits of Mackinac, instead continuing to pipe oil through the open water while it awaits permits to move the pipeline into the proposed tunnel. Devised in 2018 to alleviate concerns that Line 5 could rupture in the Great Lakes, the tunnel plan has long fueled debate between those who see it as a crucial pipeline safety project, and those who favour a permanent Line 5 shutdown.

Tensions have flared in recent weeks amid a flurry of competing decisions tied to the tunnel proposal.

On July 15, EGLE issued key permits for the tunnel project, angering Line 5 opponents who saw the move as a betrayal by Whitmer, who campaigned for office on a vow to shut down Line 5.

Two weeks later, on July 31, the Michigan Supreme Court vacated a separate tunnel permit issued by the Michigan Public Service Commission, ruling that the commission had not adequately considered environmental impacts or alternatives to digging the tunnel.

The ruling forces the Public Service Commission to rework its review, likely adding years of delay to the tunnel project.

It also sets a precedent for other state environmental reviews, requiring broad analyses of how proposed projects impact natural resources and the public’s right to use and enjoy the Great Lakes.

Tunnel opponents have argued the EGLE permit can’t withstand that kind of closer review. The Bay Mills Indian Community plans to appeal the permit, said Debbie Chizewer, an Earthjustice lawyer representing the tribe.

The groups “have been saying all along that the tunnel is a tactic by Enbridge to divert attention away from the threat of Line 5 that exists today,” said David Holtz, coalition coordinator for the group Oil & Water Don’t Mix. “Now the governor’s saying it, too.”

Tunnel supporters criticized Wednesday’s announcement, saying the project is needed to protect the Great Lakes, maintain energy access and support construction jobs.

“Governor Whitmer’s actions to further delay the Great Lakes Tunnel Project are puzzling, and a slap in the face of every skilled tradesperson who has supported her,” said Brent Pilarski, business manager of the Michigan Laborers District Council. “Politicians often speak on affordability, sustainability and protecting the middle class. The Great Lakes tunnel accomplishes that and more.”

Whitmer’s and Roos’ Wednesday announcement does not revoke the EGLE permit. However, Roos said conditions EGLE added to the permit prevent construction from moving forward until “legal questions are resolved.”

In her Wednesday letter to Enbridge outgoing CEO Gregory Ebel, Whitmer questioned whether the tunnel will ever be built and urged Ebel to find a way to transport Enbridge’s petroleum without relying on Line 5.

Citing past analyses that have concluded a Line 5 shutdown would have little impact on energy access, Whitmer urged Ebel to “pursue an alternative to both the existing dual pipelines and the tunnel, and to begin that work now.”

“For years, Enbridge has responded to concerns about the existing pipelines by pointing to the proposed Great Lakes Tunnel, while insisting the status quo is perfectly safe,” Whitmer wrote. “That argument was difficult enough to accept before July 31. It is untenable now.”

The renewed shutdown push comes six years after Whitmer first ordered Enbridge to stop using the Straits segment after a series of anchor strikes damaged the pipeline and stoked fears that it could cause a catastrophic oil spill in the Great Lakes.

Enbridge has defied the order while suing Whitmer in U.S. federal court on claims that Michigan has no authority to shut down a federally-regulated pipeline. US District Court Judge Robert Jonker ruled in Enbridge’s favor in December. Michigan state appealed in January and briefing is underway.

Separately, Attorney General Dana Nessel is seeking a shutdown in state court. That case is paused pending the outcome of Enbridge’s legal battle with Whitmer.

This Associated Press story was published September 10, 2026, by The Canadian Press.