A long-running battle over an oil pipeline beneath the Great Lakes has entered a new phase after the Michigan Supreme Court erased a key state approval for Enbridge Energy’s Line 5 project. In a 6 to 1 decision issued July 31, the justices ruled that the Michigan Public Service Commission did not complete the environmental and public trust analysis required before approving a replacement pipeline segment in 2023. The decision gives Tribal Nations and environmental groups another opportunity to challenge a project they say threatens sacred waters and treaty-protected resources. It also sends one of the region’s most disputed energy projects back to state regulators.
The ruling does not permanently cancel Enbridge’s plan for a roughly four-mile tunnel beneath the Straits of Mackinac, where Lakes Michigan and Huron meet. Instead, the court vacated the commission’s approval and returned the case for proceedings that follow its instructions. Enbridge may seek approval again, but regulators must address questions they previously treated too narrowly. Until that review is completed, the project faces renewed uncertainty.
The Court Found Serious Gaps in the Review
Enbridge wants to replace two existing underwater pipes with a new 30-inch pipeline inside a concrete-lined tunnel below the lakebed. Line 5 was built in 1953 and extends about 645 miles from Superior, Wisconsin, to Sarnia, Ontario. The system can transport up to 540,000 barrels of crude oil and natural gas liquids each day. The commission’s authority covered the replacement pipeline segment, while separate state and federal agencies are responsible for other tunnel permits.
Michigan regulators conditionally approved the segment in December 2023, finding that the tunnel would reduce the danger of an anchor striking the pipeline. The Supreme Court said the commission failed to determine whether the project would extend Line 5’s operating life and create additional environmental harm. The justices also found that regulators compared alternatives inconsistently and did not properly consider effects on public trust resources, including fishing and boating. The commission had relied partly on a 1953 finding that Line 5 served a public need, but the court ruled that this did not excuse a complete modern environmental review.
Tribal Nations Say Sacred Waters Deserve More
The challenge included the Bay Mills Indian Community, Little Traverse Bay Bands of Odawa Indians, Grand Traverse Band of Ottawa and Chippewa Indians, and Nottawaseppi Huron Band of the Potawatomi. For Anishinaabe communities, the Straits are far more than an energy corridor. The waters carry deep cultural and spiritual meaning and support treaty-protected fishing, hunting, and gathering. Tribal leaders have argued that government decisions involving the Straits must account for those rights and the state’s obligation to protect public waters.
Bay Mills Indian Community President Whitney Gravelle said the decision creates another opportunity to “honor our treaty rights, protect our waters, and consider the generations” who will inherit the region. Her statement reflects why the dispute cannot be reduced to engineering plans and energy statistics. Opponents say building the tunnel could preserve Line 5 for decades while creating years of construction in a sensitive freshwater passage. Earthjustice, which represents Bay Mills with the Native American Rights Fund, says construction could continue for more than six years.
Enbridge Still Calls the Tunnel the Safer Option
Enbridge maintains that Line 5 operates safely and that placing a new pipeline inside the tunnel would add significant protection. The company says the concrete structure would sit below the lakebed, shield the pipe from anchors, and improve access for inspection and maintenance. It also argues that Line 5 supplies fuel and propane used by homes and businesses across the Midwest and Great Lakes region. Those safety and energy arguments helped persuade the Public Service Commission when it approved the project in 2023.
The Supreme Court did not decide that the tunnel can never be built, nor did it order regulators to reject Enbridge’s application. It ruled that promised safety improvements cannot replace the wider analysis demanded by the Michigan Environmental Protection Act and the public trust doctrine. The commission must now examine the project’s full consequences, compare alternatives consistently, and consider how extending Line 5 could affect protected waters and public uses. Enbridge has said it is reviewing its legal options, while Tribal Nations are preparing to present their objections again.
For the Tribal Nations, the ruling is a major victory rather than the final word. Other permits and lawsuits involving Line 5 remain part of the wider conflict, but this decision removes a central state approval from Enbridge’s path. It confirms that Michigan must consider more than whether a tunnel can be engineered beneath the Great Lakes. Regulators must also confront what the project could mean for Line 5’s lifespan, treaty-protected lifeways, and waters held in trust for future generations
