LOS ANGELES (AP) — Police across the country are increasingly monitoring car licenses plates, compiling giant databases of ordinary citizens and their daily comings and goings.

Privacy advocates are trying to get those files open to the public, but so far their efforts have been rejected. The latest was a tentative ruling in California against a tech entrepreneur who wants access to government records collected via license plate scans.

On Thursday, a judge said San Diego's regional planning agency could deny Michael Robertson's request under California's open records law because the information pertains to law enforcement investigations.

The rapidly expanding systems and their growing databases have been the subject of a larger debate pitting privacy rights against public safety concerns in a new frontier over high-tech surveillance. A Los Angeles judge ruled in August that city police and sheriff's departments don't have to disclose records from the 3 million plates they scan each week.

Robertson, best known for creating the music website MP3.com, stepped into the discussion with a personal lawsuit, asking for access to only his information. He will still get to present his case Friday, despite the initial ruling from San Diego Superior Court Judge Katherine Bacal that went against him.

The ACLU of Southern California and the Electronic Frontier Foundation had been seeking a week's worth of data from databases that hold hundreds of millions of scans.

The license plate scanning systems have multiplied across the U.S. over the last decade, funded largely by Homeland Security grants. They're governed by a patchwork of local laws and regulations that have not yet standardized how they're used and who has access to the information they collect.

About seven in 10 law enforcement agencies used license plate scanners in 2012 and an overwhelming majority planned to acquire such systems or expand their use, according to a study by the Police Executive Research Forum, a research and policy group.

Privacy advocates say these files need to be open to public scrutiny to prevent government overreach and unconstitutional privacy invasions.

"If I'm not being investigated for a crime, there shouldn't be a secret police file on me" that details "where I go, where I shop, where I visit," Robertson said in an interview with The Associated Press prior to the ruling. "That's crazy, Nazi police-type stuff."

On the other side are government and law enforcement officials who say they're not misusing the systems and that tracking and storing the data can help with criminal investigations, either to incriminate or exonerate a suspect.

"At some point, you have to trust and believe that the agencies that you utilize for law enforcement are doing what's right and what's best for the community, and they're not targeting your community," Los Angeles County Sheriff's Sgt. John Gaw said.

In San Diego's case, records are kept for up to two years, but other agencies keep them five years or more and are limited mainly by server space.

"If that information is deleted or purged too quickly, then we lost that, and we can never go back," said Lt. Karen Stubkjaer of the San Diego Sheriff's Department.

In Robertson's case against the San Diego Association of Governments, he was seeking access to a sweeping system that links police, sheriffs and eight other law enforcement agencies. The San Diego sheriff's department has made 9.8 million scans since the system was introduced in 2009, Stubkjaer said.

He said he has no problem with officials using the technology for legitimate purposes like tracking down stolen cars. But he says license plate readers are ripe for abuse, and there's no reason for long-term storage of data on innocent people.

"I want a strong police force," he said. "But I also want my personal freedom."

Neither ruling set legal precedent, but are part of a growing debate.

"License plate readers are part of a larger conversation," said Chuck Wexler, head of the Police Executive Research Forum. "Technology is changing how the police view crime, and it is raising a number of public policy issues: How long do you hold on to this information? And what part of this information should the public have access to?"

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Tami Abdollah can be reached at http://www.twitter.com/latams