The police are spying on you.

As staff writer Marnie Eisenstadt reported, 19 police agencies in Central New York are tracking your movements through the use of license plate readers mounted on the trunks of patrol cars. Plate numbers are immediately compared against a database of unregistered and stolen cars and owners with warrants out for their arrest. A "hit'' from a license plate reader even stopped a kidnapping in progress, says the Onondaga County Sheriff's Office.

What's wrong with that? Nothing, if it ends there.

But it doesn't end there. It's up to each police department, from tiny Jordan to Onondaga County, to decide how long to keep the data and how to use it. Privacy advocates are rightly worried that millions of records kept on innocent people may be stored indefinitely and used against them at some point in the future.

Even though the technology is not new, New York has no laws governing the use of plate readers and what is done with the data they collect. Legislators and Gov. Andrew Cuomo need to remedy that.

We should ask law enforcement to justify the need to collect license plate data. State and federal grants largely are paying for the cameras, which suggests they have something to do with homeland security. But no one has articulated a rationale for collecting so much data on the movements of innocent Americans.

Law enforcement should explain why data should be kept beyond the few minutes it takes to see if the car is stolen or the driver is wanted. How long can it be used to charge someone with a crime? If there's sufficient reason to store the information, keep it in a secure lock box that only can be opened with a warrant. After a prescribed period of time, it should be virtually shredded.

Furthermore, police departments should publicly and proactively state the rules under which they operate license plate readers: who has access to the information, under what conditions it can be shared and how they make sure their own rules are being followed.

New Hampshire, the "Live Free or Die'' state, has banned license plate readers over privacy concerns. Maine lets police keep the data for 21 days. Onondaga County stores the data for a year. State Police keep it for five years. A proposed federal law would end this patchwork of rules but it is not likely to pass anytime soon. So New York should come up with its own rules.

In an election year, law-and-order legislators may be worried about being seen as anti-cop. They should be more worried about being seen as anti-privacy. Revelations about National Security Agency's spying on Americans shook us up. We've been far too complacent about invasions of our personal privacy, our freedom of association and our freedom of speech. We must strike back at government's unwarranted, unlimited snooping into our whereabouts.