They asked nicely at first. After an Immigration and Customs Enforcement agent shot and killed Renee Good, a 37-year-old mother of three who’d recently moved to Minneapolis, local law enforcement officials requested a partnership with the federal government to investigate the case, as they’d done in past shootings involving federal agents.When the Trump administration refused to cooperate, Minnesota prosecutors ratcheted up their efforts. They sent a series of strongly worded legal letters demanding evidence in the Good shooting as well as the shootings of Julio Cesar Sosa-Celis, a Venezuelan immigrant who was wounded a week after Good was shot, and Alex Pretti, who was killed on Jan. 24.Still, the administration rebuffed the requests.This week, prosecutors from Hennepin County and the state of Minnesota took the next step to force the Trump administration’s hand. They filed a federal lawsuit against the departments of Homeland Security and Justice over the evidence in the shootings, an action that Hennepin County Attorney Mary Moriarty, whose jurisdiction covers Minneapolis, characterized as “unprecedented in American history.”The Trump administration has declined to release the names of the agents involved in the shootings, even after the Minnesota Star Tribune and ProPublica identified the officers involved in the Good and Pretti incidents.“The federal government has refused to cooperate with state law enforcement, which is unique, rare and simply cannot be tolerated,” Minnesota Attorney General Keith Ellison told reporters. “[We] can’t sit around and let them do it.”In the standoff over evidence, the case has already become a game of constitutional chicken over states’ rights versus federal immunity, a battle that will have implications for others who wish to hold agents in the president’s immigration surge criminally accountable. So far, neither side is showing signs of backing down, foreshadowing a fight that could take years. If prosecutors do eventually file charges against federal agents involved in the shootings, legal experts said the path to trial, much less winning convictions, will be filled with legal and procedural challenges.“State prosecutors across the country are going to be watching what happens in Minnesota really closely,” said Alicia Bannon, director of the judiciary program at the nonprofit Brennan Center for Justice.The first test for prosecutors, if they file charges, would be to prove the agents don’t qualify for immunity through the Constitution’s supremacy clause, a rarely invoked legal doctrine that protects federal officers from state prosecutions if they’re acting lawfully and within the scope of their duties.Failing to pass that test would likely end the case.The U.S. Supreme Court hasn’t taken up a case involving supremacy clause immunity in over 100 years, Bannon said, and judges have come down differently on legal issues related to its application. There’s no easy answer as to whether Minnesota will be able to get past a supremacy clause defense, said Jill Hasday, a constitutional law professor at the University of Minnesota.“That depends on the facts, but probably the odds are stacked against it,” she said.Even if they survive such a fight, the cases could be dogged by a series of logistical challenges. Moriarty, who has been leading the investigations, has decided not to seek reelection and will leave office at the end of the year. That means whoever wins the election for her seat in November could inherit the prosecutions. In addition to not having the names of the agents, prosecutors don’t know where those agents are now. Minnesota may need to extradite them, potentially from a MAGA-leaning state that may balk at sending them to Hennepin County to stand trial. “Will the federal government or other states cooperate with that? I think the answer to that is sort of iffy,” said Ilya Somin, a law professor at George Mason University in Virginia. (Indeed, in a case involving a doctor charged with illegally mailing abortion medication to a Louisiana woman, the state of California has rejected an extradition request, citing its own laws protecting doctors from prosecution elsewhere.)The fight is focused on three shootings. But Moriarty’s office has opened criminal investigations into 14 additional cases of potentially unlawful behavior by federal agents during Operation Metro Surge, which started in early December and has wound down over the past few weeks. The other cases Moriarty is examining involve allegations of excessive force or other misconduct by federal agents, such as an incident in early January in which agents allegedly used force on staff and students on the grounds of a high school.Prosecutors are also investigating Gregory Bovino, the outgoing Border Patrol commander who helped to lead immigration surges into several American cities and who was seen on video lobbing green-smoke canisters into crowds at a park in Minneapolis.