LANSING – The fate of Michigan’s long-running battle over the Line 5 oil pipeline moved to the nation’s highest court Tuesday, as the U.S. Supreme Court heard arguments in a procedural dispute that could determine where the legal fight over the controversial pipeline will unfold.
At issue before the justices is not whether Line 5 should be shut down, but whether Michigan’s lawsuit against pipeline owner Enbridge belongs in state court or federal court — a technical question with potentially major consequences for the pipeline’s future.
Michigan Attorney General Dana Nessel filed suit in 2019 seeking to decommission the section of Line 5 that runs beneath the Straits of Mackinac, the narrow waterway connecting Lakes Michigan and Huron. Nessel argues the pipeline violates Michigan’s public trust doctrine and poses unacceptable environmental risks.
Enbridge contends the case raises federal issues involving interstate and international pipelines and should be heard in federal court.
The Supreme Court’s eventual decision will determine which court system decides the merits of Michigan’s claims — a ruling that legal experts say could influence the trajectory of one of the Midwest’s most closely watched energy disputes.
Why the Venue Matters in the Line 5 Case
The legal battle centers on whether Enbridge properly moved the case from state court to federal court after Michigan filed its lawsuit.
Federal law generally requires defendants to seek removal within 30 days of being served. Lower courts ruled Enbridge missed that deadline and ordered the case back to state court. The company argues federal jurisdiction applies regardless of timing because the pipeline operates across state and international boundaries.
While procedural, the question carries weight.
A state court venue could provide Michigan more leverage under state environmental law and public trust doctrine arguments. A federal court venue could emphasize federal oversight of interstate energy infrastructure and pipeline safety regulations.
The Supreme Court’s review reflects broader tensions between state authority and federal jurisdiction over major infrastructure projects that cross borders.
What Is Line 5?
Line 5 is a 645-mile pipeline built in 1953 that transports crude oil and natural gas liquids from Superior, Wisconsin, through Michigan, to Sarnia, Ontario.
The most controversial section consists of twin 20-inch pipelines resting on the lakebed beneath the Straits of Mackinac.
The straits sit at the heart of the Great Lakes, which contain roughly 20 percent of the world’s surface fresh water and supply drinking water to millions of people in both the United States and Canada.
Enbridge says Line 5 safely transports hundreds of thousands of barrels of petroleum products daily and plays a key role in regional fuel supplies, including propane used in parts of Michigan’s Upper Peninsula.
The company has proposed building a tunnel beneath the lakebed to house a replacement segment of the pipeline, arguing it would significantly reduce spill risks.
Environmental and Safety Concerns
Opponents of Line 5, including environmental organizations and several Native American tribes, argue the aging pipeline poses a serious threat to the Great Lakes.
Concerns intensified after a 2018 anchor strike damaged the protective coating of the pipeline in the Straits. Although the pipeline did not rupture, critics say the incident demonstrated the vulnerability of the infrastructure in one of the most sensitive freshwater ecosystems in the world.
Studies modeling worst-case spill scenarios have suggested oil released in the Straits could spread rapidly due to strong, shifting currents, potentially affecting both Lake Michigan and Lake Huron shorelines.
Tribal leaders have also argued that a spill would threaten treaty-protected fishing rights and cultural resources tied to the waters.
Supporters of the pipeline counter that Enbridge has enhanced monitoring, installed additional supports, and implemented safety upgrades. The company maintains the pipeline is safe to operate and that shutting it down would disrupt energy supplies and increase fuel costs.
How Michigan’s Lawsuit Began
In 2019, Nessel filed a lawsuit seeking to revoke and terminate the 1953 easement that allows Line 5 to operate in the Straits.
The state argues the pipeline constitutes a public nuisance and violates the public trust doctrine, which holds that certain natural resources — including navigable waters — are preserved for public use and cannot be impaired by private interests.
Enbridge challenged the state’s authority and moved the case to federal court, triggering the jurisdictional dispute now before the Supreme Court.
Separate legal and regulatory proceedings involving the tunnel proposal and federal agencies continue alongside the court battle.
What Happens Next?
The Supreme Court is not expected to rule immediately. A decision could come later this term.
The justices’ ruling will not directly determine whether Line 5 continues operating. Instead, it will decide which court system — state or federal — will hear Michigan’s claims seeking to shut down the pipeline in the Straits.
For Michigan residents, environmental advocates, tribal communities and energy stakeholders, the venue question could shape the next phase of a dispute that has stretched across multiple administrations and sparked intense debate about energy security, environmental protection and state authority.
As the legal fight moves forward, the stakes remain tied to a stretch of pipeline resting beneath the currents of the Straits of Mackinac — and to the future of infrastructure operating within one of the world’s largest freshwater systems.
