Last week, the U.S. Supreme Court heard a case that threatens police officers with financial ruin if they make arrests and the charges don’t hold up.

It began with a disorderly Washington, DC, party. The police made the decision to arrest the partygoers for trespassing.

The charges were later dropped, because it wasn’t clear beyond a reasonable doubt the partygoers knew they were trespassing. But 16 of them turned around and sued the police for false arrest and violating their constitutional rights.

They never claimed the police verbally or physically abused them. They sued simply for having been arrested, cuffed and hauled to the police station. Amazingly, the lower courts slapped the police with nearly $1 million in damages and legal fees — one of numerous recent lower-court decisions making officers personally liable for decisions made on duty.

Twenty-six states and the federal Justice Department are weighing in with a strong warning that allowing the lower-court ruling to stand would have “vast consequences” for law enforcement everywhere. On the other side, the American Civil Liberties Union is pushing to limit or even eliminate the police’s legal immunity. The ACLU wants police to have no room for error, The New York Post reports.