A federal appeals court this week ruled that a California police officer can be held liable for injuries suffered by an unarmed man he Tasered during a traffic stop. The decision, if allowed to stand, would set a rigorous legal precedent for when police are permitted to use the weapons and would force some law enforcement agencies throughout the state — and presumably the nation — to tighten their policies governing Taser use, experts said.

Michael Gennaco, an expert in police conduct issues who has conducted internal reviews of Taser use for the Los Angeles County Sheriff’s Department and other agencies, said the ruling by the U.S. 9th Circuit Court of Appeals prohibits officers from deploying Tasers in a host of scenarios and largely limits their use to situations in which a person poses an obvious danger.

“This decision talks about the need for an immediate threat. . . . Some departments allow Tasers in cases of passive resistance, such as protesters who won’t move,” he said. Tasering for “passive resistance is out the door now with this decision. Even resistance by tensing or bracing may not qualify.”