The Supreme Court delivered a unanimous decision against Enbridge Energy, ruling that the Canadian pipeline operator missed a critical deadline to move Michigan's lawsuit into federal court. Justice Sonia Sotomayor wrote that Enbridge waited 887 days to attempt the maneuver, far exceeding the 30-day requirement. The aging Line 5 pipeline runs beneath the Straits of Mackinac, connecting Lake Michigan and Lake Huron.

Michigan officials have long sought to decommission the pipeline, warning of potential environmental catastrophe if a leak occurs in the Great Lakes. The state filed suit in 2019 under the Michigan Environmental Protection Act, arguing that continued operation would likely cause pollution of water and other natural resources. Attorney General Dana Nessel has called the pipeline "a ticking time bomb in the heart of the Great Lakes."

Enbridge had argued that federal court was the appropriate venue since the pipeline network crosses borders and involves foreign affairs, supplying refineries and production plants throughout the region before terminating in Ontario. The company warned that shutting down Line 5 could raise fuel costs and threaten infrastructure used to provide heat for millions of people. While the Supreme Court's ruling addressed only the narrow procedural question of jurisdiction, it represents a significant victory for Michigan in its ongoing battle to decommission the pipeline and potentially sets a precedent for state authority over fossil fuel infrastructure.

The dispute has strained U.S.-Canada relations and scrambled traditional political alliances in the region, where the industry provides jobs but faces increasing environmental scrutiny.