The Canadian and US chambers of commerce joined forces with their counterparts in Ohio, Michigan and Wisconsin by filing a joint brief in court to argue against Gov. Gretchen Whitmer's bid to shut down the cross-border pipeline. The following day, Whitmer and Eichinger wrote to Enbridge Executive Vice President Vern Yu that if the company continues operating the pipeline, she will consider all resulting profits to be property of the state of MI and that it will be trespassing on state property.
On May 11, Enbridge announced it would defy Whitmer's shutdown orders and would only cease operations if ordered by a court or company regulator.
Enbridge Senior Vice President Mike Fernandez tells CTV News that Line 5 the does not have to stop operating while a legal process is underway in the United States.
"The scale and impact of a Line 5 oil spill would be an unprecedented ecological and economic disaster", said Liz Kirkwood, executive director of Traverse City-based For Love of Water.
A roughly 4-mile (6.4-kilometer) segment divides into two pipes that cross the Straits of Mackinac, which connects Lake Huron and Lake Michigan. A 2018 study by Michigan Tech showed that a spill in the straits could affect hundreds of kilometres of shoreline and dozens of species.
Enbridge argues Line 5 is safe, and is seeking to build a tunnel under the straits to house the pipeline.
"Thats in the courts", she said, "so were not going to have anything to add".
The fight has sparked tension between USA and Canadian officials, with Prime Minister Justin Trudeau raising the issue - albeit unsuccessfully - with U.S President Joe Biden.
The so-called "chambers brief" followed a similar filing Tuesday by the federal Liberal government, a rare global foray into US legal proceedings, that urged the court to keep the pipeline running and the two sides to reach a settlement. "Canada relationship has been successfully managed for generations", Ottawa said.
Eyre said Saskatchewan has been working with the federal government on this and helped with that brief.
Line 5 is a crucial energy artery not only for Ontario and Quebec, but for MI and surrounding states as well - all depending on it for gasoline, propane for heating homes and jet fuel. Companies have made contingency plans to transport products, but a long-term closure of the pipeline could cause logistical difficulties, experts say.
It's unlikely that anything is going to be decided until a judge in either state or US federal court makes a decision, a process that could take several months, said James Coleman, a pipeline law expert and associate professor at Southern Methodist University in Dallas.
It also says shutting down that line contravenes a 1977 treaty between the two countries. The State is arguing that its case belongs back in state court.