The documents mark Canada's formal entry into the legal dispute between MI and the pipeline's owner and operator, Calgary-based Enbridge Inc., which comes on the eve of the deadline imposed last November by Gov. Gretchen Whitmer.
According to the Michigan Advance, state officials will need a court order to shut down the pipeline on Wednesday, as Enbridge says it will not comply with Whitmer and Canadian officials have lined up behind the company.
If Whitmer eventually gets her way, a Line 5 shutdown could mark the first time a major in-service oil pipeline is forced to shutter because of environmental concerns.
A court-ordered negotiation is underway, with the two sides scheduled to meet again May 18, several days after Whitmer's self-imposed deadline.
"Today, Canada filed an amicus curiae (friend of the court) brief in the U.S. District Court for the Western District of MI". The company said Line 5 will continue to operate safely while it focuses on plans to construct a 6.4-kilometre tunnel to replace the lines beneath the straits.
Michigan Attorney General Dana Nessel filed a lawsuit last fall in support of Whitmer's order, while Enbridge countersued in federal court and wants the matter decided there.
Enbridge has "imposed on the people of MI an unacceptable risk of a catastrophic oil spill in the Great Lakes that could devastate our economy and way of life", Whitmer said when announcing the easement, which was granted despite the fact that the federal government generally regulates oil pipelines.
"The closure of Line 5 could prove to be disastrous for thousands of residents of Michigan, Ohio and the entire region", USW Local 912 president Justin Donley said.
"Energy security, economic prosperity, and supporting energy workers are top priorities for the Government of Canada", said the Honourable Seamus O'Regan.
But worldwide trade lawyer Lawrence Herman says that the United States, not MI, is legally bound to keep the pipeline running. But, in 2010 a different pipeline operated by Enbridge, Line 6B, ruptured and released petroleum into a tributary of the Kalamazoo River, becoming one of the largest inland oil spills in US history. "It supports both Canadian and American jobs".
Nessel's office said it will continue seeking a shutdown order.
Instead, Granholm was preoccupied with the fallout from a different pipeline problem: the massive Colonial line, a delivery system for almost half the fuel consumed on the U.S. East Coast, which has been shut down since Thursday following a devastating cyberattack from overseas. The country's natural resources minister called keeping the pipeline open a "non-negotiable" item, and entreaties have been made to the White House to intervene.
For almost 67 years, Enbridge has moved oil and natural gas from western Canada through MI and the Great Lakes to refineries in the province of Ontario.
It is for the two national governments, under the terms of that treaty, to sort out the dispute, the documents argue.
John Flesher/AP An aboveground section of Enbridge's Line 5 at the Mackinaw City, Michigan, pump station.
Sonya Savage, Eyre's Alberta counterpart, warned of the potential for a lingering chill if Whitmer is successful. "But what is the most concerning to us in Alberta - as it should be for everyone - is the risky precedent that a shutdown of a safely operating pipeline would set for future oil and gas infrastructure projects".
Not everyone in Canada, however, opposes Whitmer's efforts. A number of Indigenous groups in Ontario support a shutdown, as does Green party Leader Annamie Paul.
The latest issue is an order by the governor of the state of MI to shut down a Canadian line that passes through the state.
Line 5 under the Straits has never had a leak, although other Enbridge pipelines have, including one in 2010 that sent roughly 1 million gallons of oil into the Kalamazoo River in west MI.
Note to readers: This is a corrected story.