Full Breakdown
Michigan Supreme Court Vacates Permit for Enbridge Line 5 Tunnel Project
8/1/2026, 9:45:27 PM
Core Event
On July 31, the Michigan Supreme Court issued a 6-1 decision overturning the Michigan Public Service Commission’s (MPSC) approval of a key permit for Enbridge Energy’s proposed tunnel beneath the Straits of Mackinac. The justices held that the commission’s environmental review was too narrow, failing to assess whether the tunnel would extend the operational life of Line 5 and to compare the project’s impacts with viable alternatives. The ruling sends the permit back to the MPSC for a comprehensive reassessment under the Michigan Environmental Protection Act (MEPA) and the state’s public-trust doctrine.
Background & Context
Line 5 is a 645-mile pipeline that carries crude oil and natural-gas liquids from Superior, Wisconsin, to Sarnia, Ontario. A four-mile dual-line segment runs on the lakebed of the Straits of Mackinac. Since 2018, Enbridge has proposed drilling a concrete-lined tunnel 60–250 feet beneath the lakebed to house a single 30-inch pipe, shutting down the aging surface pipes. The MPSC approved the tunnel permit in December 2023 after a decade-long review. Opponents—including several tribal nations and environmental groups—argued that the commission’s analysis omitted broader environmental risks of keeping Line 5 in service.
Key Legal Findings
- “We conclude that the PSC erred by not examining whether the replacement project would be the proximate cause of further environmental harms by extending Line 5's lifespan,” — Justice Elizabeth Welch
- Public-Trust Doctrine – The court found the commission did not evaluate whether the tunnel would “pollute, impair, or destroy” the Great Lakes, which are held in trust for the public under Michigan law.
- Alternative Analysis – The justices noted the commission applied a narrow view of spill risk for the tunnel while taking a broader view for alternatives such as rail or truck transport, resulting in an inconsistent comparison.
- Dissent – Justice Brian Zahra argued the majority over-reached, asserting the commission should receive deference for its expertise and that the record was “enormous” and beyond the court’s capacity to re-evaluate. He maintained the tunnel would not increase pollution.
Official Statements & Responses
- Enbridge – Expressed disappointment, emphasizing that the tunnel would make an already safe pipeline “even safer” and reaffirming its commitment to safe operation.
- Tribal Leaders – Whitney Gravelle, president of the Bay Mills Indian Community, hailed the decision as a victory for treaty rights and Great Lakes protection.
- Legal Analysts – Attorney David Scott, representing the Environmental Law & Policy Center, called the opinion “the most important” under MEPA in decades.
Criticism & Opposition
Tribal nations and environmental groups argue the tunnel would lock in continued fossil-fuel transport, extending the life of a 73-year-old pipeline and threatening the ecological integrity of the Great Lakes. They also cite potential disturbance to burial sites, wetlands, and rare species.
Data & Statistics
- Line 5 transports roughly 540,000 barrels of light crude oil and natural-gas liquids per day across the Straits.
- A 2017 state-commissioned report estimated a 1-in-60 chance of a break by 2053.
What’s Next
The MPSC must conduct a new environmental review that determines whether the tunnel would extend Line 5’s operational life, evaluates all reasonable alternatives consistently, and assesses impacts on public-trust resources. The revised decision will be subject to further judicial oversight, and additional state and federal permits—including a pending U.S. Army Corps of Engineers authorization—remain required before construction can commence.
