LOS ANGELES (AP) — Advocacy groups have appealed a judge’s ruling that denied them access to police records of license plate scans in Los Angeles, saying they are crucial to understanding the scope of government surveillance.

The American Civil Liberties Union Foundation of Southern California and the Electronic Frontier Foundation want one week of records collected by the Los Angeles Police Department and Los Angeles County Sheriff’s Department in August 2012 — an estimated 3 million scans. Superior Court Judge James Chalfant denied the request in August, saying the records are exempt from disclosure under California’s open records law because they pertain to law enforcement investigations, and releasing them could violate individual privacy.

The groups said in a filing this week to California’s 2nd District Court of Appeal that the records are collected indiscriminately and could be used to track anyone, including political activists. It says they could be used to monitor peaceful protests, houses of worship or a particular neighborhood or organization.

“A network of readers enables police to collect extensive location data on an individual, without his knowledge and without any level of suspicion,” they wrote.

Police have expanded their use of automated license plate scanners across the U.S. over the past decade, largely with federal grants. The ACLU and Electronic Frontier Foundation estimate that the police and sheriff’s departments in Los Angeles store an average of 66 scans on each of the 7.6 million vehicles registered in the county.

Courts have only recently considered whether police can refuse to release the scans. A San Diego Superior Court judge ruled last month that technology entrepreneur Michael Robertson wasn’t entitled to see records collected on his vehicle because they pertained to law enforcement investigations. Robertson argued he isn’t a criminal suspect — at least as far as he knows — and has said he plans to appeal.

Law enforcement officials say they’re not abusing the scanners and that storing the data helps criminal investigations, either to incriminate or exonerate suspects.

A spokeswoman for the Los Angeles Police Department, Officer Norma Eisenman, declined to comment on the appeal. A spokeswoman for the sheriff’s department didn’t immediately respond to a message.