DETROIT — Lawyers for Michigan’s former health director are urging an appeals court to quickly stop an effort to revive criminal charges related to the Flint water crisis of 2014-15.

Nick Lyon’s defense team made the plea this week in response to a pledge by prosecutors to try to save indictments that were declared invalid by the Michigan Supreme Court. It’s the latest volley in the legal saga.

The attorney general’s office lost a unanimous Supreme Court decision in June, and a Genesee County judge subsequently dismissed charges against Lyon and six other people. But prosecutors are refusing to give up.

They argue the indictments, an uncommon tool in state court, can instantly be turned into traditional criminal charges, a losing argument so far. They said they’ll appeal Judge Elizabeth Kelly’s Oct. 4 ruling.

“The Michigan Supreme Court has already decided, both explicitly and implicitly, the issue in the order that the prosecution now appeals. The indictment is void and must be dismissed,” Lyon’s attorneys, Chip Chamberlain and Britt Cobb, told the appeals court.

“There are no charges remaining to remand,” they wrote.

State-appointed managers switched Flint’s water source to the Flint River in 2014, but the water wasn’t treated to reduce its disastrous impact on old pipes. As a result, lead contaminated the system for 18 months.

Lyon had no role in the water switch. But the river water was blamed for an outbreak of Legionnaires’ disease, which is typically caused by bacteria spreading through cooling systems.

Lyon and former chief medical executive Eden Wells were charged with involuntary manslaughter in nine deaths. They were accused of failing to timely warn the Flint area about the outbreak.

Former Gov. Rick Snyder was charged with two misdemeanors for his handling of the water crisis. Citing the summer Supreme Court decision, he is seeking to have his indictment dismissed, a request that is pending with a different judge in Genesee County.

An effort to hold people criminally responsible for Flint’s water mess has lasted years and produced little. Seven people pleaded no contest to misdemeanors that were eventually scrubbed from their records.

If the appeals court wants additional argument in Lyon’s case, he hopes it will act soon.

“Director Lyon is in his seventh year of dealing with these sensational and highly publicized allegations that have now been dismissed — now twice,” his attorneys wrote. “Justice has been the opposite of swift for him.”