The Supreme Court unanimously ruled Wednesday that a long‑running fight over Michigan’s Line 5 oil pipeline must return to state court, with Justice Sonia Sotomayor writing that Enbridge “waited too long” to move the case to federal court.
The decision revives Michigan’s bid to shut down a pipeline beneath the Great Lakes at a moment when energy security, environmental risk and state authority are colliding nationwide.
The ruling affects Enbridge Energy, Michigan officials and regional communities by clearing the way for state judges to decide the pipeline’s future and potentially reshape how similar energy disputes are handled.
What Is Line 5 and Why Michigan Wants It Shut Down?
The decision leaves intact a lower-court ruling that returned the case to a Michigan judge and allows the state’s lawsuit to continue in state court as it seeks to block operation of a key segment of Line 5, a petroleum pipeline that has transported crude oil and natural gas liquids between Superior, Wisconsin, and Sarnia, Ontario, since 1953.
Michigan Attorney General Dana Nessel filed the lawsuit in June 2019, asking a state court to void the easement that allows Enbridge to operate a roughly 4.5-mile section of Line 5 beneath the Straits of Mackinac, the waterway connecting Lake Michigan and Lake Huron. Nessel, a Democrat, argued the pipeline poses an unacceptable risk to the Great Lakes.
An Ingham County judge issued a restraining order in June 2020 ordering the pipeline shut down, though Enbridge was permitted to continue operating after meeting certain safety requirements.
Enbridge sought to move the case to federal court in 2021, contending the dispute raised federal issues involving cross‑border energy transportation. But in June 2024, a three-judge panel of the 6th U.S. Circuit Court of Appeals ruled that Enbridge missed a 30‑day deadline to change jurisdictions, sending the case back to state court. The Supreme Court agreed.
Concerns about Line 5 have intensified in recent years after Enbridge disclosed that it had been aware of gaps in the pipeline’s protective coating beneath the straits since at least 2014. In 2018, a ship’s anchor struck the underwater section, heightening fears of a potential spill in one of the world’s largest freshwater systems.
Enbridge told Newsweek in a statement that the safety of Line 5 is regulated exclusively at the federal level by the pipeline and Hazardous Materials Safety Administration, an agency within the U.S. Department of Transportation, which conducts annual inspections of the pipeline and has consistently found it to be in compliance.
The company said that PHMSA oversees Line 5’s operations across the Straits of Mackinac and has identified no safety concerns that would justify shutting it down.
What Happens Next
The case returns to Michigan state court, where judges will decide whether the state can force the shutdown of the Line 5 pipeline segment beneath the Straits of Mackinac. Michigan officials say the aging pipeline threatens the Great Lakes, while Enbridge argues it remains safe and critical to regional energy supplies and will continue operating it while the case proceeds.
Separately, Enbridge is fighting Michigan Democratic Governor Gretchen Whitmer’s 2020 decision to revoke the pipeline’s easement in a federal case, where the company has proposed enclosing the underwater section in a protective tunnel. Although state regulators approved permits for that project in 2023, key federal approvals remain unresolved.
The pipeline also faces a separate legal challenge in Wisconsin, where a federal judge has ordered Enbridge to shut down a segment crossing tribal land unless it is rerouted, a ruling the company is appealing.
“Pipeline safety is, and always has been, the responsibility of the federal government under a comprehensive regulatory framework administered by PHMSA,” an Enbridge spokesperson said. “That agency inspects Line 5 annually, has consistently confirmed it operates safely and has never found any condition that would warrant its shutdown. We remain fully committed to the safe operation of Line 5 and to working constructively with regulators and stakeholders as this process continues.”
Supreme Court Unanimous Rulings: What to Know
Despite the Supreme Court’s sharp ideological divisions in many high‑profile cases, unanimous rulings are relatively common. According to SCOTUSblog’s end‑of‑term Stat Pack released in June 2025, covering the October 2024 term, about 42 percent of the court’s opinions were decided unanimously.
Such outcomes are especially frequent in cases involving procedural deadlines, jurisdictional rules or technical questions of statutory interpretation, court watchers say—areas where justices often agree even as they remain divided on broader constitutional issues.
Reporting by the Associated Press contributed to this article.
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