Supreme Court Hands Michigan Major Win in Line 5 Pipeline Battle

In a unanimous decision issued on Wednesday, April 22, 2026, the U.S. Supreme Court ruled in favor of Michigan, marking a critical turning point in the state’s years-long effort to shut down the aging Line 5 energy pipeline.

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The ruling is a procedural blow to Enbridge, the Canadian energy firm behind the pipeline, as it forces the legal battle back into state court—a venue the company has fought hard to avoid.

The Legal Turning Point: A Matter of Timing

The high court’s decision hinged on a procedural error by Enbridge. Writing for the Court, Justice Sonia Sotomayor clarified that the company missed its legal window to move the case to a federal level:

• The 30-Day Rule: Federal law generally requires companies to request a move to federal court within 30 days of being served.
• The 887-Day Delay: Enbridge waited nearly two and a half years before attempting the move.
• The Ruling: The Court rejected Enbridge’s argument for an exception, emphasizing that legal “threshold questions” must be settled early to ensure judicial efficiency.

What’s at Stake in the Straits of Mackinac?

At the heart of the dispute is a 72-year-old section of the pipeline spanning the Straits of Mackinac, the waterway connecting Lake Michigan and Lake Huron.

• Environmental Risks: State officials and tribal nations argue the pipeline is a “ticking time bomb,” warning that a rupture would cause an ecological and economic catastrophe in the Great Lakes.
• Energy Supply: Enbridge maintains that the line—which moves 23 million gallons of crude oil and natural gas daily—is essential for energy security in Ontario and parts of the U.S. Midwest.

Why the Venue Shift Matters

This move back to state court is a strategic victory for Attorney General Dana Nessel. While federal courts have historically favored federal oversight of interstate pipelines, the state court allows Michigan to pursue the shutdown based on state-specific public nuisance and environmental protection laws.

What Happens Next?

Despite this ruling, Line 5 remains operational as several parallel legal battles continue:

1. Pending Appeals: Michigan is currently appealing a separate 2025 federal ruling that claimed the state lacks the authority to interfere with the line.
2. The Tunnel Solution: Enbridge is still pushing for a “Great Lakes Tunnel” project to house a new section of the pipe beneath the lakebed. This project is currently awaiting its own fate in the Michigan Supreme Court.