Michigan Supreme Court orders new review of Enbridge Line 5 tunnel permit

Michigan’s Supreme Court has ordered regulators to take another look at a key permit for Enbridge’s plan to build a tunnel for its Line 5 oil pipeline beneath the Straits of Mackinac, the narrow channel where Lakes Michigan and Huron meet. The 6–1 ruling sends the project back to the Michigan Public Service Commission after tribal nations and environmental groups challenged a 2023 approval. Enbridge says the tunnel would protect the Great Lakes while keeping energy supplies reliable in the region.

The court’s complaint was not about whether the pipeline moves oil today, but about what the tunnel would lock in for decades. According to the Independent, the justices said regulators failed to grapple with whether the tunnel project would extend the pipeline’s lifetime, and therefore its cumulative environmental risk. They also faulted the commission’s comparisons to alternatives such as transporting oil by truck or train, calling the reasoning inconsistent. The ruling further says the agency did not adequately assess impacts on fishing, boating, and other public trust rights tied to the Great Lakes.

That pushes a familiar North American infrastructure fight into its most expensive phase: years of legal process before anyone pours concrete. Enbridge has argued the tunnel would “massively” reduce spill risk compared with the existing line, which runs along the bottom of the straits. Opponents counter that the location is both environmentally sensitive and culturally significant, describing the straits as a sacred site for Anishinaabe tribes and warning that construction itself would bring noise, vibration, and long disruption.

The case also exposes how permits can become a substitute for policy decisions that elected officials do not want to price directly. Governor Gretchen Whitmer and other state officials have been trying since 2020 to shut down the straits segment through separate litigation, while the company has pursued a tunnel proposal that has been under review for nearly a decade, according to the Independent. Each delay preserves the status quo: oil continues to flow, but the cost of deciding—through courts, consultants, and regulators—keeps rising.

Enbridge said it is reviewing legal options after the decision. The tunnel plan now returns to the same state commission that approved it, with the court instructing regulators to answer questions they previously left out of the record.