Lansing − The United States and Canadian governments asked a federal appellate court Friday to block Michigan’s efforts to shut down Enbridge’s Line 5 oil pipeline beneath the Straits of Mackinac.
The Department of Justice told the Sixth Circuit Court of Appeals that the state’s efforts to close line would threaten an affordable supply of energy for Americans, would tread on federal interests in pipeline safety and impinge on the U.S.’s relationship with Canada, which previously invoked a treaty over Michigan’s threats.
“The United States has a manifest interest in complying with its treaty obligations with all sovereigns, and in avoiding potential monetary liability if it is found to have breached those obligations,” the U.S. said in its filing.
The U.S.’s brief was filed in a pending appeal in the Sixth Circuit Court of Appeals, where Michigan is attempting to reverse a December 2025 U.S. District court decision that found federal pipeline safety laws preempt Michigan’s efforts to close the line.
The Friday filing marked the second time the Trump administration has officially waded into the years-long Line 5 legal fight; the Department of Justice also filed a statement of interest when the case was in district court last year. Additionally, Trump’s predecessor, Democratic President Joe Biden, also expressed concerns over how a Line 5 shutdown would affect U.S.-Canada relations in a Wisconsin case seeking the pipeline’s closure.
Democratic Gov. Gretchen Whitmer, who’s been largely silent on the Line 5 issue in recent years, wrote a blog post Friday criticizing Trump’s intervention in the case.
“Today, our federal government took Enbridge’s side in court,” Whitmer said. “They argue that Michigan has no say in whether an oil company runs an aging pipeline through our Great Lakes.”
The filings in the federal appeal come the same day the Michigan Supreme Court overturned approvals Enbridge had been given by a state regulatory body to relocated Line 5 into a tunnel beneath the Straits of Mackinac. The high court decision will delay tunnel construction, potentially for years, leaving the current controversial 73-year-old twin spans sitting on the bottomlands at the nexus of Lakes Huron and Michigan.
The case at issue stems back to 2020, when Whitmer ordered Line 5 closed and filed a suit attempting to enforce that order. Enbridge countersued and Whitmer’s case was dismissed. One other suit seeking Line 5’s closure, filed by Attorney General Dana Nessel in 2019, remains alive in state court.
In 2021, Canada invoked a never-before-used 1977 treaty between the U.S. and Canada to prevent Michigan from shuttering the line. Negotiations have been ongoing since.
In Enbridge’s federal countersuit, which is the one on appeal in the Sixth Circuit, the company made an array of arguments for the pipeline’s continued operation. But most of those arguments centered around the idea that the federal government has sole authority over pipelines and any efforts to shutter the line would have lasting effects on international relations with Canada.
In December 2025, U.S. District Judge Robert Jonker agreed with Enbridge, finding federal pipeline safety preempts Michigan’s legal efforts to shutter the pipeline.
Congress expressly has jurisdiction of pipeline safety through the Pipeline Safety Act of 1992, Jonker wrote, and both the U.S. and Canada agree that the state’s attempt “interferes with their explicit federal foreign policy positions and trade relations.”
“Pipeline safety generally, and protection of the Straits of Mackinac, are critical interests to be sure,” Jonker wrote. “But when it comes to Line 5, they are the responsibility of the United States and Michigan lacks the power to interfere.”
Whitmer and Nessel appealed Jonker’s decision to the Sixth Circuit Court of Appeals, where the U.S. and Canada and various business groups filed Friday in support of Enbridge.
The U.S. argued the Pipeline Safety Act and Foreign Affairs Doctrine, under the supremacy clause, both stand in the way of Michigan taking adverse action on a pipeline or action that would harm the nation’s relationship with Canada.
“Recognizing that a 50-state patchwork of pipeline safety requirements would be untenable, Congress expressly preempted state safety standards for interstate pipelines,” the U.S. said in its filing.
Canada, in its filing, argued a shutdown would harm U.S.-Canada relations and Canadian residents that rely on the oil and natural gas transported over Line 5.
The Canadian government further noted that it’s 1977 transnational pipeline treaty with the U.S. was critical context in which to consider Michigan’s threat to the pipeline.
“The treaty preempts the shutdown order,” Canada said of the treaty it invoked in 2021. “It is self-executing, and it prohibits ‘public authorities’ from ‘interfering’ with the ‘uninterrupted transmission’ of hydrocarbons through transit pipelines. No exception to that prohibition applies here.”
The 73-year-old twin span beneath the Straits of Mackinac transports about 540,000 barrels of light crude oil and natural gas liquids a day, and has long been a cause for concern among environmental groups and some government officials, who fear the catastrophic effects of an oil spill in Lakes Michigan and Huron. Supporters of the pipeline have warned against closing the line out of concern for potential natural gas and oil shortages in Canada and the Midwest.
Nessel and Whitmer both campaigned in 2018 on promises to shutter the line even as Republican former Gov. Rick Snyder, as he was leaving office, entered a deal with Enbridge requiring the Calgary, Alberta-based company to build a $500 million tunnel beneath the straits to house a new section of the pipeline.
Enbridge recently secured its last state-level permits for the project. But the Friday Michigan Supreme Court opinion revoking its Michigan Public Service Commission approvals will create significant delays in tunnel construction.
eleblanc@detroitnews.com
This article originally appeared on The Detroit News: U.S., Canada file in support of Line 5 as Michigan seeks its closure
Reporting by Beth LeBlanc, The Detroit News / The Detroit News
USA TODAY Network via Reuters Connect
By Beth LeBlanc, The Detroit News | USA TODAY Network
