A Virginia man has sued the Fairfax County Police Department (FCPD) and its chief of police, alleging that the agency has been "unlawfully" collecting information about his license plate in violation of state law.

The lawsuit, which was filed Tuesday by the American Civil Liberties Union (ACLU) of Virginia on behalf of Harrison Neal, marks a unique legal challenge to the use of automated license plate readers (LPR) by local law enforcement. In 2014, Neal asked via a public records request for all instances in which his car had been read by the FCPD LPR system; the agency provided documentation showing that he had been seen twice in 2014.

The case alleges that the FCPD, through its "passive" collection and storage of massive amounts of data (license plate number, date, time and GPS location) contravenes the Virginia Data Act of 1976. Passive collection is distinct from the FCPD’s "active" use of the data, when it scans an unknown plate against a "hot list" of wanted or stolen vehicles and determines that the unknown plate is part of an ongoing criminal investigation.

In Virginia, the state’s own attorney general has previously said in a 2013 letter to the head of the state police that such active collection violates the Data Act. Neal now wants the court to order forbid the FCPD from continuing its passive scanning, where it routinely collects and stores thousands of LPR records on a daily basis.

"The Department’s ALPR database can be used to discover the location of thousands of vehicles at a particular date and time," Rebecca Glenberg, the ACLU of Virginia’s legal director said in a statement. "It is an unacceptable invasion of privacy. The Data Act is very clear. Personal information cannot be collected, stored, or disseminated unless the need for such collection has been clearly established in advance and the information is appropriate and relevant for the purpose for which it was collected. None of this is true of the thousands of license plate numbers stored in FCPD’s database."

Earlier this year, Ars obtained 4.6 million LPR records collected by the police in Oakland, California over four years, and just 0.16 percent of those reads were "hits." We discovered that such data is incredibly revelatory—we were even able to find the city block where a member of the city council lives, using nothing but the database, a related data visualization tool, and his license plate number.

One of the controversial issues with respect to LPR collection is how long the data is kept. Absent an explicit policy, this can be an indefinite period of time. In Virginia, such policies are determined by individual agencies, and as such, vary widely. Gov. Terry McAuliffe (D) vetoed a bill just last week that had been passed unanimously by both the Virginia General Assembly and Senate that would have set such a limit at seven days, absent an ongoing criminal investigation. Given the bill’s veto, those standards can now remain variable throughout the state.

The FCPD did not immediately respond to Ars’ request for comment.