Michigan Supreme Court Vacates Line 5 Tunnel Permit

On July 31, 2026, the United States — Michigan Supreme Court, in a 6-1 decision, vacated the United States — Michigan Public Service Commission's December 2023 approval of a key permit for Enbridge's Line 5 tunnel project under the United States — Straits of Mackinac. The court found that the commission's environmental review was overly narrow, failed to consider whether the tunnel would extend the pipeline's life and associated harms, inconsistently compared alternatives, and neglected to assess impacts on public trust resources in the Great Lakes. The case was remanded to the commission for a broader review. The ruling is a victory for tribal nations and environmental groups that challenged the permit, and it further delays the project, which has been in regulatory limbo for eight years. Enbridge expressed disappointment and is assessing legal options. The decision does not order the pipeline shut down, but it adds another hurdle to the project's permitting process.