SAN FRANCISCO (AP) - A federal appeals court says law enforcement must provide a valid reason to hold people's vehicles and cannot automatically impound them for a set period.

The unanimous ruling on Wednesday by a three-judge panel of the 9th U.S. Circuit Court of Appeals struck down a California law that requires police to hold impounded vehicles for 30 days.

Judge Alex Kozinski, writing for the panel, said the law violates the Fourth Amendment prohibition against unreasonable seizures. He said police cannot continue to hold a seized vehicle without some new justification.

The decision revived a lawsuit against Los Angeles by a woman whose car was held by city police for 30 days. The Los Angeles City Attorney's office did not immediately have comment.