SPRINGFIELD, Ill. (AP) — The Illinois Supreme Court says Chicago can keep all records of complaints about police officers, no matter how old they are.

The court ruled 6-1 on Thursday that state law trumps a provision of the police union’s contract with the city that calls for records more than five years old to be destroyed.

The ruling, which upheld a lower court’s decision, is a major victory for police reform advocates, who say the records are crucial to any effort to monitor officers with a history of complaints.

The president of the police union says the union may appeal to the U.S. Supreme Court.