Enbridge’s aging Line 5 pipeline, which runs beneath the Straits of Mackinac in the Great Lakes, continues to raise environmental and regulatory concerns as debates over its future intensify. The pipeline, in operation for more than seven decades, carries oil from Alberta, Canada, to Sarnia, Ontario, crossing environmentally sensitive areas in Michigan.

Line 5 is one of two major pipelines owned by Enbridge in the region; the other, known as Lakehead Line 78, follows a route that circumvents the Great Lakes. While Line 5’s sub-lake segment has drawn criticism for its potential spill risks, Line 78 has been rebuilt and expanded following the 2010 Kalamazoo River spill and is seen by some experts and officials as a safer and feasible alternative for transporting oil.

The Michigan Supreme Court’s recent decision to vacate a permit for a tunnel intended to house and protect Line 5 beneath the Straits was welcomed by environmental groups and state officials who view the move as a step toward shutting down the pipeline. The ruling came shortly after a leak in Wisconsin prompted renewed calls from Michigan Governor Gretchen Whitmer to end Line 5’s operations. Whitmer has urged Enbridge to find alternative routes outside of the Great Lakes within a matter of months, emphasizing the environmental risks posed by Line 5.

Enbridge has previously rerouted oil shipments to Line 78 during Line 5 shutdowns, demonstrating operational flexibility and reinforcing arguments that the older pipeline may no longer be essential. Critics argue that continued reliance on Line 5 jeopardizes the Great Lakes, which hold approximately 20% of the world’s fresh surface water and serve as a critical resource for both U.S. and Canadian communities, including numerous tribal nations.

The Mackinac Bridge Walk in 2026, led by tribal groups and environmental advocates, underscored the cultural and ecological importance of protecting the Great Lakes from potential oil spills. The event highlighted widespread calls to decommission Line 5, with some voices urging Michigan’s incoming governor, set to take office in January 2027, to prioritize terminating the pipeline’s operation.

Enbridge and supporters of Line 5 emphasize the economic benefits tied to the pipeline, noting that the infrastructure generates billions of dollars in revenue over decades. However, opponents maintain that the potential environmental damage and risks posed to the Great Lakes outweigh these profits. The debate continues as stakeholders weigh energy needs, economic factors, and environmental protection in a region where the future of the pipeline remains uncertain.