If you frequent gun shows, especially those in American towns near the Mexican border, your personal information may have been gathered and stored by local police and federal agents through the license plate on your car while you were inside. And it could still be going on.

According to this story from the Wall Street Journal, federal agents have persuaded police officers to scan license plates to gather information about gun-show customers. The story says the information comes from government emails and raises questions about how officers monitor what are completely legal, constitutionally protected activities.

The newspaper reviewed emails it was given that indicate agents with the Immigration and Customs Enforcement Agency (ICE) crafted a plan in 2010 to use license-plate readers at gun shows in Southern California, including one in Del Mar near the Mexican border.

License plate readers are devices that record the plate numbers of all passing cars, similar to the cameras at toll booths that scan the tags of cars without transponders that go through an EZ pass toll lane.

The story says agents then compared that information to cars that crossed the border, hoping to find gun smugglers.

From the story:

The investigative tactic concerns privacy and guns-rights advocates, who call it an invasion of privacy. The law-enforcement officials say it is an important and legal tool for pursuing dangerous, hard-to-track illegal activity.

“There is no indication the gun-show surveillance led to any arrests or investigative leads, but the officials didn’t rule out that such surveillance may have happened elsewhere. The agency has no written policy on its use of license-plate readers and could engage in similar surveillance in the future, they said.

“WSJ spoke to Jay Stanley, a lawyer at the ACLU, who said the gun-show surveillance “highlights the problem with mass collection of data,” adding that law enforcement can take two entirely legal activities, like buying guns and crossing the border, “and because those two activities in concert fit somebody’s idea of a crime, a person becomes inherently suspicious.”

Gun owners of America executive officer Erich Pratt told the paper his group also opposes such techniques.

“Information on law-abiding gun owners ends up getting recorded, stored, and registered, which is a violation of the 1986 Firearm Owners Protection Act and of the Second Amendment,” Pratt said in the story.

Even John Chigos, the CEO of PlateSmart Technologies, Inc.—the company sells the license plate reader systems—is against police and federal agents using the tech in this manner, calling it “an abuse of the technology” to target gun-show shoppers, in the story.

“I think this was a situation that shows we need to establish policies for license-late readers, like any new technology,” he told the Wall Street Journal.

Police use license plate readers more and more to search for fugitives and missing children. The technology was recently employed to help locate the man who allegedly set of a bomb in New York City recently, the story says.

The story points out that police officers have long been allowed to legally record license plates they observe in the course of ordinary life. But the new technology allows that kind of observation to become high-speed mass-data collection, since a single camera can record thousands of vehicle plates in an hour, at high speeds and in thick traffic—conditions in which no human being could do the same.

From the story:

“Critics such as Mr. Pratt say using the technology for gun shows is illegal in any case because of the firearm owners act, which bans the government from creating records of gun buyers except temporarily for background checks.

“The Journal obtained, through a request under the Freedom of Information Act, internal ICE emails showing agents in 2010 targeted a gun show called Crossroads of the West in Del Mar, Calif.

“More than half of the pages provided by the agency were completely redacted, or blacked out; others have large sections redacted, apparently to keep secret how the surveillance was undertaken.

“In an email titled “Request for Assistance,” an ICE investigator wrote, “We would like to see if you can support an outbound guns/ammo operation on (redacted) at the Crossroads (Del Mar) Gun Show. We would like to deploy license plate readers.” The email, whose sender and recipient are redacted, includes a large section of operational details that are also redacted.

“The law-enforcement officials with knowledge of the operation confirmed ICE got local police officers to drive around the parking lot at the gun show and use their license-plate readers to collect all of the cars’ information. A spokeswoman for the San Diego County Sheriff’s Office declined to comment on whether the department took part in the activity.”

The paper also spoke to Bob Templeton, the CEO of Crossroads of the West, which puts on the gun show. He said he knew local police had been at the show, but was surprised to learn federal agents had been gathering data about the 6,000 to 9,000 customers the show draws.

“It’s obviously intrusive and an activity that hasn’t proven to have any legitimate law-enforcement purpose,” Templeton said in the story. “I think my customers would be resentful of having been the target of that kind of surveillance.”