Michigan’s Top Court Orders Regulators to Reassess Enbridge Pipeline Tunnel Permit

Michigan’s highest court ruled Friday that state regulators must reexamine a critical permit authorizing construction of an underground tunnel for a major oil pipeline beneath the Great Lakes. The 6-1 decision by the Michigan Supreme Court creates significant uncertainty for Enbridge’s Line 5 project, a 73-year-old conduit operated by Canadian energy firm Enbridge that transports petroleum from Superior, Wisconsin, to Sarnia, Ontario.

The disputed section of Line 5 spans 4 miles along the bottom of the Straits of Mackinac, where Lakes Huron and Michigan converge. Enbridge seeks to bury the existing pipeline within a tunnel to shield it from environmental hazards, while Michigan Gov. Gretchen Whitmer and environmental advocates contend the line should be relocated away from the waterway entirely, citing catastrophic spill risks to the Great Lakes ecosystem.

The Michigan Public Service Commission approved the tunnel permit in 2023, but four tribal nations and environmental organizations immediately challenged the decision in court. The state Supreme Court determined that regulators failed to examine whether the tunnel would extend the pipeline’s operational lifespan and thereby increase cumulative environmental harm over time.

Justices also found that the commission inadequately evaluated alternative transportation methods such as trucks or rail, and neglected to assess potential impacts on fishing, boating, and other public rights tied to the Great Lakes. The Straits of Mackinac hold sacred significance for the Indigenous Anishinaabe peoples, who oppose using the location as a construction zone for years.

David Gover, an attorney with the Native American Rights Fund, stated that pumping more than 500,000 barrels of oil daily through the Great Lakes’ center—whether suspended in water or encased in a tunnel—remains fundamentally flawed. Enbridge spokesperson Ryan Duffy expressed disappointment over the delay in a project under regulatory review for nearly a decade, asserting the tunnel would enhance environmental safeguards while preserving regional energy security.

The company proposed the tunnel approximately nine years ago following an incident in which a ship anchor damaged part of the line. Enbridge maintains that underground installation would substantially reduce spill probability, though opponents warn that tunnel construction would generate noise, vibrations, and lasting environmental degradation beneath the straits.

In parallel litigation, Michigan’s governor and state officials have pursued efforts since 2020 to shut down the pipeline entirely under the straits, adding another layer of legal complexity to the project’s fate.