DETROIT (AP) — The Michigan Supreme Court on Wednesday rejected a last-chance effort to revive criminal charges against seven people in the Flint water scandal, waving away an appeal by prosecutors who have desperately tried to get around a 2022 decision that gutted the cases.

The attorney general’s office used an uncommon tool — a one-judge grand jury — to hear evidence and return indictments against nine people, including former Gov. Rick Snyder. But the Supreme Court last year said the process was unconstitutional, and it struck down the charges as invalid.

State prosecutors, however, were undeterred. They returned to Flint courts and argued the charges could be easily revived with a simple refiling of documents. That position was repeatedly rejected all the way to the state’s highest court.

“We are not persuaded that the question presented should be reviewed by this court,” the Supreme Court said in a series of one-sentence orders Wednesday.

Orders were filed in cases against former state health director Nick Lyon, former state medical executive Eden Wells and five other people.

Snyder was charged with willful neglect of duty, a misdemeanor. The indictment against him has also been dismissed, though the Supreme Court did not address an appeal by prosecutors Wednesday only because that case is on a different timetable.

Managers appointed by Snyder turned the Flint River into a source for Flint water in 2014, but the water wasn’t treated to reduce its corrosive impact on old pipes. As a result, lead contaminated the system for 18 months.

Lyon and Wells were charged with involuntary manslaughter. Some experts have attributed a fatal Legionnaires’ disease outbreak in 2014-15 to the water switch. They were accused of not warning the public in a timely manner.

Indictments were also thrown out against Snyder’s former chief of staff, Jarrod Agen; another key aide, Rich Baird; former Flint Managers Gerald Ambrose and Darnell Earley; former city Public Works Director Howard Croft; and former health official Nancy Peeler.

Snyder, a Republican, acknowledged that state government botched the water switch, especially regulators who didn’t require certain treatments. But his lawyers deny his conduct rose to the level of a crime. The former governor recently called it “political persecution.”

Prosecutors could try to start from scratch. But any effort to file charges in a more traditional way against some targets now could be barred by Michigan’s six-year statute of limitations.

The attorney general’s office released a statement that said it would explore how to share evidence with the public “who most deserve to know the truth,” but that could require a change in law. It didn’t explicitly say what it would do next beyond that.

“The evidence supporting the felony charges remains sealed and the statutes involved make it a misdemeanor to release any of the information,” prosecutors said.

Flint Mayor Sheldon Neeley said dismissal of the indictments was an “unfair victory” for the defendants “based on a technicality.”

Defense attorneys had a different view.

William Swor said he hopes prosecutors now “will let Mr. Ambrose live the rest of his life in peace.”

And Randall Levine said the state committed a “travesty” in charging Baird, who was accused of perjury, obstruction of justice, misconduct in office and extortion. He denied any wrongdoing.

Since 2016, the attorney general’s office, under a Republican and now a Democrat, has tried to hold people criminally responsible for Flint’s water disaster, but there have been no felony convictions or jail sentences. Seven people pleaded no contest to misdemeanors that were later scrubbed from their records.

The Michigan Civil Rights Commission in 2017 said the water switch was the result of systemic racism, doubting that the brush-off of complaints about the poor quality of the river water would have occurred in a white, prosperous community. Nearly 57% of Flint residents are Black.

Separately, the state agreed to pay $600 million as part of a $626 million settlement with residents and property owners who were harmed by lead-tainted water. Most of the money is going to children.

Flint was reconnected to a regional water system in 2015 and has been compliant with lead standards for seven years, regulators said.