Against a political backdrop of heightened public awareness of the risks Canadian tar sands oil spills might carry for  human health and the environment, Michigan governor Gretchen Whitmer took legal action this past Friday to shut down a pipeline that transports oil beneath the channel that links two of the Great Lakes.

A seemingly minor detail of the $500 million, multi-year tunnel project — getting a state commission’s permission to move a 4-mile segment of pipeline inside the tunnel— could now give environmental activists and Native American tribes an opening to litigate broad objections to the 67 year old pipeline and, they hope, shut it down completely.

Whitmer's office has notified Enbridge, the Great Lakes pipeline's operator, of its decision.  Governor Whitmer's legal counsel in the matter said  in a letter to Enbridge that "the revocation resulted from 'a violation of the public trust doctrine' and 'a longstanding, persistent pattern of noncompliance with easement conditions and the standard of due care.'”

“Enbridge has routinely refused to take action to protect our Great Lakes and the millions of Americans who depend on them for clean drinking water and good jobs,” Whitmer said in a statement. "They have repeatedly violated the terms of the 1953 easement by ignoring structural problems that put our Great Lakes and our families at risk."

"Most importantly, Enbridge has imposed on the people of Michigan an unacceptable risk of a catastrophic oil spill in the Great Lakes that could devastate our economy and way of life. That’s why we’re taking action now, and why I will continue to hold accountable anyone who threatens our Great Lakes and fresh water.”

Governor Whitmer's move escalates a multiyear battle over Line 5, which is part of Enbridge's Lakehead network of pipelines that carries oil from western Canada to refineries in the U.S. and Ontario. The pipeline carries about 23 million gallons (87 million liters) of oil and natural gas liquids daily between Superior, Wisconsin, and Sarnia, Ontario.