Federal judge rules warrantless Flock license plate search unconstitutional, calls system 'indiscriminate mass surveillance'

A federal judge in Oklahoma ruled Thursday that a police officer violated the Fourth Amendment when he searched a California woman's license plate in Flock Safety's automated license plate reader (ALPR) network without a warrant, then used her travel history to justify a vehicle search that uncovered 91 pounds of methamphetamine. The decision, which calls Flock's network "a type of indiscriminate mass surveillance," is one of the first times a federal judge has found warrantless Flock searches unconstitutional.

The officer's "use of the ALPR Systems was an Unconstitutional Warrantless Search," and "was not supported by probable cause, and it was done without a warrant in violation of [the defendant's] Fourth Amendment rights," Judge Sara Hill wrote in her opinion. Hill said the officer should have obtained a warrant before querying the Flock system. Audit logs viewed by 404 Media show more than a hundred thousand warrantless searches of the Flock system occur each month. Hill's ruling will not set binding precedent, and several other cases nationwide are examining the legality of warrantless ALPR searches.

The traffic stop and the Flock search

In May, Tulsa County Deputy Sheriff Freddie Alaniz was parked along an Oklahoma highway when he saw a Mazda SUV with a California license plate driven by Melisa Kyle. "Alaniz then pulled his vehicle on the highway to follow the Mazda for no apparent reason other than the fact that it had a California license plate. Alaniz also ran a query on the Flock system for the California license plate number on the Mazda SUV," Hill wrote. Alaniz pulled Kyle over for changing lanes without a turn signal.

During the stop, Alaniz interrogated Kyle about her recent travel "while he continued to review the ALPR systems for the car she was driving," the judge wrote. He made Kyle recount her activities from the previous several days and compared her account to the Flock data. He told her that because she was only in California for a short period, he suspected drug trafficking. The Flock travel history became part of his justification to search the car, where he found 91 pounds of meth. Hill ruled that all Flock evidence and all evidence from the search must be suppressed.

Mass surveillance and reasonable expectations of privacy

"The Fourth Amendment requires courts to draw a line when the cost is too great. Alaniz's search in just the ALPR system provided him with more than 50 individual records of Kyle's whereabouts across the country for an entire month," Hill wrote. "The Court finds that because the ALPR systems Alaniz used to search Kyle's historical location information intruded on her reasonable expectation of privacy in the whole of her physical movements, it was a search under the Fourth Amendment."

Hill directly challenged earlier court rulings that found ALPR searches do not require warrants. Those decisions leaned on the 1983 Supreme Court case United States v. Knotts, which said a person traveling on public roads has no reasonable expectation of privacy in their movements. But Hill argued "that language exists in the context of the facts presented in the case. Rather than a large-scale, dragnet-type surveillance system like the ALPR technology in this case, the Court in Knotts was confronted with much less sophisticated technology."

"The Court acknowledges that people, in at least a broad sense, do not have a reasonable expectation of privacy in their movements on a public roadway," Hill wrote. "But by virtue of how ALPR technology works, Alaniz and other officers using these systems have access to a continuously updated location history for all vehicles caught on ALPR cameras within the network. This is a type of indiscriminate mass surveillance."

Patterns of travel-based stops

The ruling highlights what civil liberties advocates describe as a recurring tactic: law enforcement flagging out-of-state plates, running them through Flock's network, and using travel patterns as a pretext for stops and searches. "We're seeing that repeatedly with police flagging whatever they'll call suspicious patterns of movement," said Michael Soyfer, a lawyer at the Institute for Justice, which is litigating several Fourth Amendment cases involving Flock cameras. "I think Flock is going to automate that using AI where cops can set alerts for those kinds of travel patterns."

Soyfer called the opinion significant. "It recognizes one thing that courts ignore which is the sheer breadth of these systems, that they collect so much information about so many people in a way that sets them apart," he told 404 Media. "This decision ascribes appropriate weight to the fact police are building out this massive database that can reveal incredibly intimate details of people's lives."

The decision comes after a separate jury verdict earlier this week in an Institute for Justice case, which found that U.S. Border Patrol license plate reader scans used by a predictive policing unit were unconstitutional. It also follows the Supreme Court's decision in Carpenter v. United States, which held that accessing a person's cell phone location data constitutes a search.

A Flock Safety spokesperson said the company was not a party to the case. "The ruling goes against the overwhelming weight of authority in similar cases across the country, including multiple recent decisions in Oklahoma, and we expect it will be appealed and ultimately overturned," the spokesperson said. "This ruling is limited to the specific facts of this case. It does not set controlling precedent and does not affect law enforcement agencies' continued use of these important public safety technologies."

Why this matters for legal and communications professionals

Hill's opinion signals that courts are beginning to grapple with the scale of ALPR networks in Fourth Amendment analysis, not just the fact that individual cameras capture public activity. For government attorneys and police legal advisors, the ruling underscores the growing risk that warrantless Flock searches will face suppression challenges - particularly when an officer's initial justification is as thin as an out-of-state license plate. Communications and PR professionals working with law enforcement agencies or surveillance technology companies should prepare for increased scrutiny of automated data collection practices and the narratives used to justify them. The legal landscape is shifting, and the argument that these systems are "cut and dry" constitutionally no longer holds uncontested.