Flock ALPR searches can require warrant, judge rules

A federal judge in Oklahoma has thrown out evidence gathered through Flock automatic license plate recognition (ALPR) cameras in a methamphetamine trafficking case. Legal experts say the decision is the clearest example so far of how the Supreme Court's June ruling on geofencing, known as Chatrie, is reshaping disputes over digital evidence.

Judge Sara Hill ruled on October 1 that a sheriff's deputy improperly relied on Flock data to build a case against Melisa Kyle. According to experts, it is one of the first times a federal judge has found that police searches of historical ALPR data can violate the Fourth Amendment, the part of the US Constitution that protects people against unreasonable searches and seizures.

The ruling is not binding precedent. It does, however, break with a long run of court decisions holding that warrantless ALPR searches are acceptable because the cameras do not follow a person's every movement minute by minute.

From a traffic stop to a month of travel history

In May 2026, Tulsa County deputy sheriff Freddie Alaniz saw Kyle's car change lanes without signaling. Because the vehicle had a California plate, he searched Flock's national database and found that Kyle had traveled extensively over the previous month.

He then pulled her over, ran further Flock searches, and questioned her about her movements based on the camera sightings. A search of the car turned up a large quantity of methamphetamine.

According to Hill's ruling, the deputy quickly found 50 separate sightings of Kyle's car across multiple states over about a month. Hill called this an "unconstitutional warrantless search" and an example of "indiscriminate mass surveillance." Because the Flock search was carried out without probable cause, the evidence found in the vehicle was ruled inadmissible.

Hill wrote that ALPR searches are "not targeted on a single individual." Instead, the system "collects information about all vehicles that pass by any network-connected camera at all times, and it serves up the information to law enforcement on demand."

She acknowledged that Flock cameras record location less precisely than cell phones. Even so, she described ALPR data collection as "persistent, dragnet-style surveillance."

Why Chatrie matters here

In Chatrie v. United States, a majority of Supreme Court justices found that police searches of historical cell phone location data held by third-party tech companies are limited by the Fourth Amendment. The case involved geofence requests, where police with no suspect ask tech companies for the location histories of everyone near a crime scene.

Before Chatrie, the court had not ruled on modern police technology and the Fourth Amendment since 2018. In that case, Carpenter v. United States, the justices held that police need a warrant to use cell site location data to track a specific suspect.

Hill cited Chatrie repeatedly. Courts have long held that drivers on public roads have no reasonable expectation of privacy, but she rejected that argument for long-term tracking. "Cell phones also move in public places where people can see you in plain view," her opinion noted. ALPRs become "constitutionally problematic," she wrote, when police "can indiscriminately and passively catalog your whereabouts over an extended period of time and then use that information for any purpose whenever convenient."

Andrew Ferguson, a professor at George Washington Law School, called the case "a direct result of Chatrie." He said Hill "chose to view ALPRs as a tracking system that can capture the whole of one's movements and not just a fancy camera that catches numbers and letters." Ferguson added that it is the first time a court has said ALPR searches require a warrant in some circumstances.

Chatrie is already appearing in other courts. In August, a Mississippi federal judge cited it in ruling that cell tower dumps are unconstitutional general warrants.

Flock pushes back

Robert Frommer of the Institute for Justice said the Chatrie factors fit ALPRs "to a T" and expects the Oklahoma decision "to be the first of many to come." His group is suing Norfolk, Virginia, over Flock searches. The judge in that case found ALPRs do not meet the "whole of movements" standard, and the case is now under appeal.

Sidney Thaxter of the National Association of Criminal Defense Lawyers said ALPR networks "allow police to retroactively track our whereabouts with the press of a few buttons." Tom Bowman of the Center for Democracy and Technology argued that the ALPR "business model is built on exactly the kind of retrospective tracking the Supreme Court has said requires a warrant."

A Flock spokesperson said the ruling "goes against the overwhelming weight of authority in similar cases across the country" and that the company expects it to be "appealed and ultimately overturned." The company stressed that the decision is limited to the facts of the case and does not affect agencies' continued use of the technology. Oklahoma authorities have not yet said whether they will appeal.

Why It Matters

For privacy and security readers, the key point is how Hill described the technology. She treated Flock as a searchable tracking database, not as a set of roadside cameras. This suggests courts may start judging surveillance tools by the data they pile up over time rather than by what a single sensor captures at one moment.

The ruling fits a wider shift. Chatrie has already been used against cell tower dumps, and lawmakers are also looking at the cameras, with bipartisan ALPR bills now on the table. If more judges follow Hill, warrant requirements could make long-term ALPR lookups much less useful to police, as experts noted.

It is too early to call this a turning point. The decision is not binding, other courts have gone the other way, and an appeal is possible. It is worth watching how the Norfolk appeal turns out and whether any higher court takes up ALPR searches directly.