The U.S. Supreme Court on Wednesday sided with Michigan, ruling that the state’s lawsuit aimed at shutting down an aging Enbridge energy pipeline segment beneath the Straits of Mackinac will remain in state court. Justice Sonia Sotomayor authored the unanimous opinion that said Enbridge waited too long to ask that the case be moved to federal court.
The litigation centers on Line 5, a pipeline that has transported crude oil and natural gas liquids between Superior, Wisconsin, and Sarnia, Ontario, since 1953, and that runs under the Great Lakes waterway linking Lake Michigan and Lake Huron. Michigan’s case challenges whether Enbridge has the legal right to operate the pipeline’s underwater section.
Michigan Attorney General Dana Nessel filed the suit in state court in June 2019, seeking to void an easement that allows Enbridge to operate a 4.5-mile (6.4-kilometer) segment under the Straits of Mackinac. In June 2020, Nessel won a restraining order from Ingham County Judge James Jamo that shut down the pipeline, though Enbridge was allowed to continue operating after meeting safety requirements.
Enbridge then moved the dispute to federal court in 2021, arguing that the case affects U.S. and Canadian trade. But a three-judge panel of the U.S. Court of Appeals for the 6th Circuit sent the case back to Jamo in June 2024, ruling that the company missed a 30-day deadline to change jurisdictions.
The Supreme Court’s Wednesday ruling addressed that jurisdictional effort, and it left the state-court case in place. Enbridge issued a statement saying the judge in the Whitmer case had already decided that federal regulators—not the state—are responsible for Line 5’s safety and that regulators had found no issues warranting shutting it down.
Michigan officials have continued to press that the case should proceed under state control. Nessel said in a statement that the Supreme Court decision made “emphatically clear” that her lawsuit belongs in state court, where the state has argued since 2019 that Line 5 does not have a legal right to the Straits bottomlands.
The Supreme Court ruling arrives amid other legal battles over Line 5 and the pipeline’s safety and permitting. The Michigan Department of Natural Resources, under Gov. Gretchen Whitmer, revoked the Straits easement for Line 5 in 2020, and Enbridge filed a separate federal lawsuit challenging that revocation. Whitmer, also a Democrat, later appealed a federal judge’s decision that had blocked her revocation challenge, and the Supreme Court in March rejected Whitmer’s argument that she could not be sued in federal court.
The pipeline’s future is also tied to permitting disputes. Enbridge has sought permits to encase the Straits segment in a protective tunnel, and the Michigan Public Service Commission granted related permits in 2023. A coalition of environmental groups and Michigan tribes has sued to void those state permits for the tunnel, and Michigan’s Supreme Court is weighing that case. Enbridge also needs approvals from the U.S. Army Corps of Engineers and the Michigan Department of Environment, Great Lakes and Energy.
Separately, Line 5 remains at issue in Wisconsin. A federal judge in Madison last summer gave Enbridge three years to shut down a section of Line 5 running across the Bad River Band of the Lake Superior’s reservation, and Enbridge has appealed that shutdown order to the U.S. Court of Appeals for the 7th Circuit while it began work in February to reroute the line around the reservation. The Bad River and environmental groups have filed a state lawsuit seeking to halt the reroute construction, arguing regulators underestimated the damage the construction would cause, and that case is also pending.