The Michigan Supreme Court on Friday vacated a central state approval for Enbridge’s proposed Line 5 tunnel, ruling that regulators improperly narrowed their environmental review and failed to fully consider harms to the Great Lakes and public trust resources.
High court demands broader analysis
In a 6-1 decision issued July 31, the justices overturned the Michigan Public Service Commission’s (PSC) December 2023 order that would have authorized a four‑mile reroute of Line 5 into a concrete‑lined tunnel beneath the Straits of Mackinac. The ruling sends the matter back to the PSC for further proceedings and reopens questions about whether constructing the tunnel would extend the operating life of the entire 645‑mile pipeline.
Writing for the majority, Justice Elizabeth Welch criticized the commission for treating different environmental risks inconsistently. She noted the PSC considered greenhouse gas emissions from the pipeline “as a whole” when weighing harms, yet declined to analyze other risks — including potential oil spills — on that same comprehensive basis.
“The PSC acted inconsistently by considering greenhouse emissions from the pipeline as a whole in its harms analysis, but declining to consider other environmental risks (like oil spills) using that same scope,” the majority opinion said.
The decision strips away one of the foundational permissions Enbridge needs to begin tunnel construction and adds potentially significant time to a regulatory process that has been unresolved for roughly eight years.
What the court found and what comes next
The majority found the PSC’s permit review was overly narrow and specifically faulted the commission for failing to assess whether the tunnel would harm the state’s public trust interests in the Great Lakes and submerged lands. The court ordered regulators to consistently compare the tunnel to feasible alternatives and to separately examine harm to public trust resources.
The ruling does not itself order the shutdown of Line 5. Opponents — including a coalition of four tribal nations and a Traverse City‑based environmental group — had asked regulators to consider shutting the 72‑year‑old line rather than merely rerouting that segment into a tunnel. Their challenge contended the commission’s original analysis was flawed and incomplete.
Enbridge has argued the proposed tunnel is the safest option for protecting the Straits because it would place the pipeline in a concrete‑lined bore, reducing the risk of a spill compared with the current exposed segment on the lake bottom. Company lawyers told the court the commission correctly concluded the tunnel would best avoid a spill since the line would continue to move product one way or another.
Context and regional implications
Line 5 is a 645‑mile pipeline that carries petroleum products from Superior, Wisconsin, through northern Michigan to Sarnia, Ontario. The contested Straits segment is a four‑mile crossing where the line currently lies exposed on the lakebed, a configuration that has drawn public concern because of the Straits’ ecological sensitivity.
The pipeline runs through several northern Michigan counties, including Dickinson and Iron, on its approach to the Straits. The tunnel project has been the center of dueling legal and political battles involving Enbridge, state regulators, tribal governments, environmental groups and the governor’s office.
Notably, the court’s decision comes about two weeks after Gov. Gretchen Whitmer’s administration issued separate environmental and endangered‑species permits for the tunnel — actions that drew immediate criticism from tribes and environmental advocates, who argued the state had abandoned earlier promises to protect the lakes.
Reactions from advocates and regulators
Tribal nations and environmental organizations hailed the ruling as a correction to what they described as an inadequate review. Legal advocates had argued before the high court that the PSC’s analysis was “lopsided” and required a fuller, more balanced consideration of alternatives and harms.
David Scott, a senior attorney with the Environmental Law & Policy Center, said regulators must now “determine all the tunnel’s polluting effects on the state’s air, water and natural resources” under the Michigan Environmental Protection Act — language reflecting the court’s instruction for a broader harms analysis.
Enbridge and its attorneys maintain that the tunnel remains the best way to protect the Straits from spills and that the pipeline will be refurbished or otherwise maintained regardless of the tunnel outcome.
Practical implications and timeline
The court’s ruling reopens procedural review at the PSC and could lead to additional rounds of hearings, evidence and legal argument. Depending on the commission’s next steps and any further appeals, the process could extend for months or years, further delaying any construction start date and leaving the long‑term fate of Line 5 unresolved.
- Decision: Michigan Supreme Court vacated PSC approval (6–1).
- Project: Proposed four‑mile tunnel to reroute Line 5 under the Straits of Mackinac.
- Pipeline length: 645 miles, from Superior, Wis., to Sarnia, Ontario.
- Age of Line 5: 72 years.
| Item | Detail |
|---|---|
| Court vote | 6–1 |
| Contested segment | 4 miles under the Straits of Mackinac |
| Original PSC order | December 2023 |
The decision makes clear that state regulators must rebuild their review on firmer, more comprehensive legal footing. For communities along Line 5’s route, tribal nations asserting treaty and trust interests, and the millions who rely on the Great Lakes, the next steps at the PSC will be watched closely.
As the matter returns to the administrative arena, the practical effect is immediate: additional scrutiny, renewed legal posture and continued uncertainty about whether the pipeline will be rerouted, shut down or otherwise altered in the years ahead.
