Michigan Attorney General Dana Nessel sued in state court in June 2019 to void the easement allowing Enbridge to operate a 4.5-mile section of pipeline under the Straits of Mackinac, according to court documents. In June 2020, Ingham County Judge James Jamo issued a restraining order shutting down the pipeline, but Enbridge was allowed to continue operations after meeting safety requirements, court records show. Enbridge moved the lawsuit to federal court in 2021, arguing it affects U.S. and Canadian trade. In June 2024, a three-judge panel from the Sixth U.S. Circuit Court of Appeals sent the case back to Judge Jamo, finding Enbridge missed a 30-day deadline to change jurisdictions.
Concerns over the pipeline section rupturing and causing a catastrophic spill have grown since 2017, when Enbridge engineers revealed they knew about gaps in the protective coating since 2014, according to company disclosures. A boat anchor damaged the pipeline section in 2018, intensifying fears of a spill. The Michigan Department of Natural Resources under Governor Gretchen Whitmer revoked the Straits easement for Line 5 in 2020. Enbridge filed a separate federal lawsuit challenging the revocation. A federal judge blocked Whitmer's revocation attempt, and Whitmer has appealed to the Sixth U.S. Circuit Court of Appeals. In March, the Supreme Court rejected Whitmer's appeal claiming she couldn't be sued in federal court.
Enbridge is seeking permits to encase the pipeline section beneath the Straits in a protective tunnel. The Michigan Public Service Commission granted relevant permits for the tunnel in 2023. A coalition of environmental groups and Michigan tribes has filed a lawsuit seeking to void state permits for the tunnel, and the state Supreme Court is weighing that case. Enbridge also needs approval from the U.S. Army Corps of Engineers and the Michigan Department of Environment, Great Lakes and Energy. The pipeline is at the center of a separate legal dispute in Wisconsin.