More than 1,800 documents showed the federal immigration agency accessed data from more than 80 law enforcement groups, though two that spoke with NBC News denied the allegations.
The American Civil Liberties Union on Wednesday called on law enforcement organizations to stop sharing license plate tracking data with U.S. Immigration and Customs Enforcement.
The organization released more than 1,800 pages of documents that it said showed ICE had accessed such data from more than 80 local law enforcement groups in more than a dozen states that used automated license plate readers, or ALPRs, which have drawn criticism from privacy advocates for being an invasive way of tracking people's movements.
The findings are the result of a Freedom of Information Act lawsuit from the ACLU of Northern California. The suit sought documents related to a contract between ICE and media and technology company Thomson Reuters, which provided access to a massive automated license plate reader database maintained by Vigilant Solutions, a company that provides ALPR data and analysis to law enforcement.
One Vigilant document released by the ACLU showed a long list of police departments that had provided such data to ICE through Vigilant.
"The information that they collect nominally to protect residents is being used by ICE to destroy communities," Vasudha Talla, a staff attorney with the ACLU of Northern California, told NBC News.
A spokesperson for ICE said that the agency "is not seeking to build a license plate reader database, and will not collect nor contribute any data to a national public or private database through this contract." The spokesperson did not respond to follow-up questions about its use of Vigilant's system.
ALPRs are specialized cameras that can quickly scan license plates and are commonly used by law enforcement nationwide. A 2012 document published by the Department of Justice showed that the devices can read plates at rates of up to 1,800 per minute, or 30 plates per second.
Vigilant Solutions did not immediately respond to requests for comment. A spokesperson for Thomson Reuters declined to comment.
The Dallas Police Department, one of the departments listed in the document, confirmed that it shares data with ICE and hundreds of other law enforcement organizations nationwide. A spokesperson for the department said it has 46 ALPR devices.
Two other California police agencies, including one named by the ACLU in its press release, disputed their inclusion on Vigilant's list.
Union City Police Department spokesman Lt. Steve Mendez said that the agency does not have any license plate readers, citing their high cost. He said that the department is a Vigilant client but that it only uses the company's information and does not contribute its own.
"We do subscribe to Vigilant Solutions as a 'read only,' client, we cannot input info," he said in an email. "We use the information from that source for our own local investigations. We do not share that information with ICE. If we should get [ALPRs] in the future, we would not share information we gather with ICE."
The Vigilant document also listed the Ventura Police Department in California as another entity that shares license plate data with Vigilant, and in turn, with ICE.Ventura PD spokesman Cmdr. Tom Higgins said that his department does not have ALPRs.
While the department does occasionally receive data from the Ventura County Sheriff's Office, which maintains 34 ALPRs mounted on patrol cars, the county agency says it does not provide data to federal authorities.
"We don't have any [memorandum of understanding] with ICE or any other federal agency," Capt. Eric Hatlee, a sheroff's office spokesman, said.
The ACLU did not immediately respond to questions about the agencies' denials.
The apparent contradiction highlights the opaque world of data collection and sharing between law enforcement and private contractors that provide extensive databases of information collected from a variety of sources, including commercially.
Brian Hofer, the head of the Oakland Privacy Advisory Commission in California, said the documents released by the ACLU showed the dangers of "mass surveillance."
"What I hope a story like this impresses upon people is — how much of their data is out there, how much of it is being collected every single day by private and public entities, and the ubiquitous nature of these mass surveillance devices being used against people," he said.
Law enforcement agencies often deploy their own ALPR gear, then create and maintain their own databases. Some may even take an extra step and share the data with Vigilant Solutions, which compiles the data for use by its clients.
Under its contract with Vigilant, ICE has access to commercial license plate reader data. The documents released by the ACLU show records from ICE training agents on how they can accept or share data from law enforcement agencies.
More than 9,000 ICE officers have access to the system, according to the documents released by the ACLU. For civil immigration cases, ICE agents are allowed to search the database going back five years. For criminal investigations, ICE is allowed to search within the statute of limitations for the crime being investigated.
The ACLU argued that some of those agencies in the data sharing report could be acting in violation of local privacy laws or "sanctuary city" policies intended to protect undocumented immigrants by allowing ICE to access that information, including some in California.The ACLU said there are two 2015 state laws that local law enforcement may unwittingly be violating: the California Values Act, which prohibits state authorities from cooperating with federal immigration enforcement, and also Senate Bill 34, which specifically mandates that "dissemination of ALPR information is consistent with respect for individuals' privacy and civil liberties."
"What I think these documents show is that even with those surveillance ordinances, once a community buys surveillance tech, it's very hard to control the flow of information," the ACLU's Talla said.
As an example, she cited an email exchange revealed in the documents -- it was between an ICE agent and a Southern California detective, in which the former asks the officer to search for law enforcement license plate data.
Hofer, of the Oakland Privacy Advisory Commission, said the documents released by the ACLU showed that data sharing can make even legitimate surveillance the subject of abuse.
"When data that's collected for something else is used by a different person with different values, that's the problem that we're seeing," he added.