Michigan Supreme Court overturns key permit for Enbridge's Line 5 tunnel project, ruling the regulator violated environmental protection law and the public trust doctrine
The Michigan Supreme Court has overturned a permit authorising Enbridge Energy's proposed Line 5 pipeline tunnel beneath the Straits of Mackinac, in a significant victory for Tribal Nations and environmental advocates who had challenged the project. The court ruled that the Michigan Public Service Commission (MPSC) violated the Michigan Environmental Protection Act (MEPA) and failed to fulfil its obligations under Michigan's public trust doctrine when it approved Enbridge's tunnel permit in 2023. The ruling requires the MPSC to reconsider the application using the legal standards set out by the court. The proposed tunnel would have relocated a four-mile segment of the Line 5 oil pipeline into a tunnel beneath the Straits of Mackinac, a critical Great Lakes waterway. Enbridge had argued the tunnel would reduce the risk of an oil spill in the Straits. Tribal Nations and environmental groups opposing the project contended it would instead prolong the operational life of an ageing pipeline and threaten one of North America's most ecologically significant freshwater systems. The ruling does not terminate the project outright but sends it back to the MPSC for a fresh review applying the correct legal standards, meaning the dispute over Line 5 is likely to continue for a further regulatory and potentially judicial cycle.
Why this matters
This ruling is significant because it applies the public trust doctrine, a common law principle requiring governments to protect certain natural resources for public use, as a binding constraint on a regulatory permitting decision, not merely as a policy aspiration. The court's finding that the MPSC violated environmental protection law in approving the permit raises the bar for future energy infrastructure approvals in Michigan and potentially signals how other Great Lakes states might approach similar pipeline and tunnel permit applications. For Tribal Nations, the outcome reinforces treaty-based and environmental standing to challenge infrastructure decisions that threaten ecologically or culturally significant waterways.
On the Ground
This matter primarily engages public law and environmental litigation (judicial review of regulatory permitting decisions, public trust doctrine pleading), natural resources law (pipeline regulation, environmental impact assessment), and indigenous rights law (Tribal Nation treaty rights and standing in environmental challenges). While the jurisdiction is Michigan rather than England and Wales, the public trust doctrine has direct analogues in UK environmental and public law, making the reasoning relevant to trainees advising on UK infrastructure disputes. A trainee on a comparable UK matter would assist with preparing chronologies of the regulatory approval process, researching environmental statutory frameworks, and reviewing the administrative record for grounds of challenge.
Interview prep
Question you might get
“What is the public trust doctrine, and how might it be applied to challenge an energy infrastructure approval in a UK or European context?”
Sign up free to see the full answer
A model answer you can lift into an interview — how to frame this story for a partner.
Sign up freeMy notes
saved