The Supreme Court ruled unanimously on Thursday that Michigan can pursue its lawsuit to close a controversial oil pipeline running beneath the Straits of Mackinac, rejecting pipeline operator Enbridge's argument that only federal regulators have authority over the dispute. The decision hands the state a major procedural victory in a fight that has stretched across nearly a decade and pits energy infrastructure against environmental risk in one of the nation's most sensitive waterways.
The case, Enbridge Inc. v. Michigan, centered on Line 5, a 72-year-old pipeline that carries roughly 540,000 barrels of oil and natural gas liquids per day between Superior, Wisconsin, and Sarnia, Ontario, passing through a four-mile underwater segment in the Great Lakes. Michigan filed suit in 2019 seeking to revoke an easement the state granted in 1953, arguing the aging pipeline poses an unacceptable risk of a catastrophic spill in the straits connecting Lake Michigan and Lake Huron.
Justice Ketanji Brown Jackson wrote the opinion for a unanimous court. The core question was whether the Pipeline Safety Act, a 1968 federal law governing pipeline safety standards, preempted Michigan's state-law claim to revoke the easement. Enbridge argued it did, contending that federal safety regulation occupied the field and barred a state from using property-law tools to effectively shut down a federally regulated pipeline.
The court disagreed. Jackson wrote that the federal law sets minimum safety standards but does not strip states of their traditional property rights over submerged lands. The ruling does not order Line 5 closed. It allows Michigan's case to proceed in state court, where the merits of the easement revocation will be litigated.
The decision drew concurrences from Justices Clarence Thomas and Neil Gorsuch, who agreed with the outcome but wrote separately to address the scope of federal preemption doctrine. Their concurrences signaled concern about the broader implications of allowing federal regulatory schemes to override traditional state property authority, a theme that resonates well beyond pipeline law. The Court's recent unanimous opinion letting oil companies move Louisiana coastal damage suits to federal court similarly reflected the justices' willingness to act with one voice in disputes at the intersection of energy and state authority.
Enbridge's Line 5 has operated since 1953, when Michigan granted the company an easement to run the pipeline across state-owned bottomlands beneath the Straits of Mackinac. The underwater segment spans roughly four miles at depths reaching 270 feet. The pipeline is a critical artery for Midwestern fuel supply, delivering light crude oil and natural gas liquids used in propane production across Michigan, Ohio, Pennsylvania, Ontario, and Quebec.
Environmental groups and Michigan officials have warned for years that the pipeline's age makes it vulnerable to rupture. A 2018 anchor strike damaged the pipeline's outer coating, heightening public anxiety. Then-Governor Gretchen Whitmer, a Democrat, revoked the easement in 2020 through executive action, but Enbridge refused to shut down operations, and the legal battle escalated.
Enbridge has proposed replacing the underwater segment with a new tunnel drilled through bedrock beneath the lakebed. The company says the tunnel project would eliminate environmental risk while preserving the fuel supply chain. Michigan regulators approved the tunnel concept, but construction has not begun, and permitting disputes have stalled progress. As the Court weighs other consequential cases this term, the Enbridge dispute stands out for the sheer scale of the infrastructure and environmental stakes involved.
Preemption is the legal doctrine holding that federal law can override state law when Congress intends to occupy a regulatory field. Enbridge leaned hard on this argument, telling the justices that the Pipeline Safety Act created a comprehensive federal safety regime and that Michigan was using property law as a backdoor to regulate pipeline safety, something only federal authorities can do.
Michigan countered that it was not trying to regulate safety at all. The state framed its claim as a straightforward exercise of property rights: it owns the lakebed, it granted an easement decades ago, and it has the sovereign authority to revoke that easement when conditions warrant. The state argued the Pipeline Safety Act's savings clause, which preserves certain state powers, supported its position.
Jackson's opinion sided with Michigan on the key structural question. The federal safety law, she wrote, does not preempt a state's exercise of its property rights over submerged lands, even when the practical effect is to threaten a pipeline's continued operation. The distinction matters: it means states retain leverage over infrastructure crossing state-owned land, a principle with implications far beyond Michigan.
Thursday's ruling does not end the fight. It sends the case back to Michigan courts, where the state must prove on the merits that it has grounds to revoke the 1953 easement. Enbridge will have every opportunity to argue that the easement remains valid, that the pipeline operates safely, and that revocation would cause enormous economic harm.
The economic stakes are substantial. Enbridge has said that shutting down Line 5 would disrupt fuel supplies across the upper Midwest and into Canada, driving up propane and gasoline prices. Canadian officials, including the government of Ontario, intervened in the litigation to oppose shutdown, arguing the pipeline is critical cross-border infrastructure protected in part by a 1977 transit pipeline treaty between the United States and Canada.
The treaty argument did not feature prominently in Thursday's ruling, which focused narrowly on federal preemption under the Pipeline Safety Act. But it could resurface in the state-court proceedings or in future federal litigation. Investigators and regulators will also need to determine whether Enbridge's proposed tunnel replacement can proceed on a timeline that satisfies Michigan's safety concerns. The justices' willingness to take on high-profile disputes this term, including the recent vacatur in the Steve Bannon contempt case, shows a court unafraid of politically charged dockets.
The tension at the heart of this case is one conservatives know well. Pipeline infrastructure is the backbone of affordable energy. Shutting down a major conduit serving millions of households and businesses carries real costs, measured in higher fuel prices, supply disruptions, and lost jobs. Enbridge has emphasized these points relentlessly, and the company's allies in the energy sector argue that Michigan's lawsuit is driven more by environmental politics than genuine safety analysis.
On the other side, the pipeline is 72 years old and runs through one of the largest freshwater systems on Earth. The Great Lakes hold roughly 21 percent of the world's surface fresh water. A major spill in the Straits of Mackinac could cause environmental damage on a scale that dwarfs previous inland pipeline disasters. Michigan officials have pointed to Enbridge's own history, including the 2010 Kalamazoo River spill, one of the largest inland oil spills in U.S. history, as evidence that the company's safety assurances deserve skepticism.
The Supreme Court did not weigh in on which side has the better argument on the merits. It answered only the threshold legal question: can Michigan bring this claim at all? The answer is yes.
For conservative legal observers, the federalism dimension of the ruling deserves attention. The Thomas and Gorsuch concurrences underscore a principle that cuts across ideological lines: states retain sovereign authority over their own property, and federal regulatory schemes should not be read to silently strip that authority without clear congressional intent.
That principle has broad applications. States own submerged lands, riverbeds, and vast tracts of territory that host federal infrastructure, military installations, and regulated industries. A ruling that federal safety regulation automatically preempted state property claims could have weakened state sovereignty in ways that extend far beyond pipelines. With speculation about Justice Alito's potential retirement and the future composition of the Court, the unanimous alignment on state property rights here may signal a durable consensus that outlasts any single justice's tenure.
Michigan Attorney General Dana Nessel called the ruling a victory for the state's right to protect the Great Lakes. Enbridge said in a statement that it remains committed to the tunnel replacement project and will continue operating Line 5 in compliance with all applicable safety regulations while the litigation proceeds.
The state-court proceedings could take years. Enbridge has deep pockets and strong incentives to delay any shutdown order while it pursues the tunnel project. Michigan will need to demonstrate not just that it has the legal authority to revoke the easement, but that doing so is justified given the current condition of the pipeline and the alternatives available.
Federal regulators at the Pipeline and Hazardous Materials Safety Administration have not publicly stated whether they believe Line 5 should be shut down. Their position, or silence, could influence the state-court proceedings. The U.S. Army Corps of Engineers also holds permitting authority over the proposed tunnel, adding another layer of federal involvement that could accelerate or stall the replacement project.
Authorities have not publicly confirmed a firm timeline for when the tunnel could be operational, even if all permits were granted tomorrow. That gap between the current pipeline's risk profile and the replacement's uncertain timeline sits at the center of the dispute.
A 72-year-old pipeline beneath the Great Lakes, a unanimous Supreme Court, and a state-court fight that could reshape the balance between energy infrastructure and state sovereignty. Whatever Michigan's courts decide on the merits, the legal framework is now clear: states still own their land, and Washington cannot quietly take that away.
