Michigan Attorney General Dana Nessel (D) has declared unconstitutional a late-2018 law that would create an authority to oversee construction of a key tunnel. The tunnel would house an oil-and-gas pipeline under the Straits of Mackinac.

The state’s Republican-led Legislature approved the law in December, and former Gov. Rick Snyder (R) signed the bill to create the Mackinac Corridor Authority. It would oversee Enbridge’s construction of a tunnel beneath the straits to replace the company’s aging Line 5 pipeline. The underwater line carries oil and natural gas to Michigan’s Upper Peninsula, as well as Wisconsin and Canada.

Current Michigan Gov. Gretchen Whitmer (D) requested the AG’s legal opinion, claiming that the law is invalid. The enabling legislation changed the bill’s original purpose, she said, because it went “beyond the scope of what was disclosed in its title.”

Republican leaders in the state Legislature scoffed at the opinion because a judge already has allowed the law to stand. That’s despite a challenge over the length of the terms of authority members, which was upheld. Consumer groups are expected to sue, as residents of the Upper Peninsula rely on propane for home heating and oppose plans that would take Line 5 out of service without replacing it.

Kelly Rossman-McKinney, Nessel’s communications director, said the attorney general feels confident the opinion will be upheld. Whitmer, meanwhile, has reopened discussions with Enbridge and hasn’t ruled out a tunnel or utility corridor to get the pipeline out of the water. But she has said it needs to be built faster than the $350-million to $500-million, 10-year timeline Enbridge promised under the Snyder-era deal. A spokeswoman for Snyder said the former governor has no comment.

“My goal is to get the pipeline out of water, and to make sure Yoopers [Upper Peninsula residents] have access to affordable energy,” Whitmer told the Detroit News.