“The legal standard basically is that a federal officer is immune from state prosecution if their actions were authorized by federal law and necessary and proper to fulfilling their duties,” said Robert Yablon, a professor at the University of Wisconsin Law School.
Yablon, who is the faculty co-director of the school’s State Democracy Research Initiative, said state prosecutors would have to consider both state and federal laws to overcome the hurdles of immunity. They would first need to show a violation of state statutes to bring charges, but also that the use of force was unconstitutionally excessive under federal law.
“If the actions violated the Fourth Amendment, you can’t say those actions were exercised under federal law,” he said, referring to the constitutional protection against unreasonable searches and seizures by the government.