A federal judge on Wednesday blocked Michigan from enforcing a 2020 order to shut down Enbridge Inc.’s Line 5 oil pipeline, ruling that the state does not have the authority to regulate pipeline safety.

U.S. District Judge Robert Jonker’s decision marks a pivotal turn in a years-long legal battle over the 72-year-old pipeline, which runs beneath the Straits of Mackinac. 

The ruling asserts that the responsibility for pipeline safety and the protection of the channel linking Lake Michigan and Lake Huron lies with the federal government, not the state of Michigan.

The dispute began five years ago when Michigan Gov. Gretchen Whitmer revoked an easement that allowed the Canadian energy company to operate a 4-mile stretch of the pipeline. 

Whitmer cited the potential for a catastrophic environmental disaster in the Great Lakes as the primary reason for the shutdown order.

Despite the state’s efforts, the pipeline has remained operational throughout the litigation, transporting approximately 540,000 barrels of crude oil and refined products daily from Superior, Wisconsin, to Sarnia, Ontario.

Enbridge has proposed a long-term solution to environmental concerns by building a tunnel beneath the lakebed to house the aging pipeline. 

Despite gaining momentum—including a "national energy emergency" status designation from the U.S. Army Corps of Engineers in April to fast-track permits, and later approving the pipeline tunnel plan in late October, the project has continued to face relentless resistance.

Environmental advocates and several Native American tribes have campaigned against the tunnel, arguing that any continued operation of the line poses an unacceptable risk to the region's water and climate.

However, the court's decision reinforces the argument that federal law preempts state intervention in interstate energy infrastructure. 

Following the court’s determination, representatives for the governor’s office did not immediately comment on whether the state intends to appeal the ruling.