Michigan Supreme Court Vacates Line 5 Tunnel Permit, Orders New Environmental Review

The Michigan Supreme Court issued a ruling vacating a permit that the Michigan Public Service Commission had granted for Enbridge's Line 5 tunnel project, a proposed pipeline segment beneath the Straits of Mackinac. The court's order directs state energy regulators to conduct a new environmental review of the project rather than allowing the existing permit to stand. The ruling was reported in early August 2026, with coverage noting it followed a period in July when Gov. Gretchen Whitmer's administration had issued key permits advancing the project toward construction. The decision is described as a significant setback for the Line 5 tunnel project, which aims to replace an aging pipeline segment with a tunnel encasement beneath the Straits. Beyond its immediate effect on Enbridge's permit, reporting indicates the ruling may have broader implications for Michigan environmental law, potentially expanding the scope of factors state agencies must consider when assessing environmental harms in permitting decisions generally. The Michigan Public Service Commission will now need to redo its environmental review process for the project as instructed by the court. The practical timeline for the Public Service Commission's renewed review, and how it will affect the overall schedule for the Line 5 tunnel project, remain unresolved based on available reporting. It is also unclear from the reports what specific new criteria or standards the commission must apply in its reassessment, or whether Enbridge or state officials have publicly responded to the ruling with plans for next steps.