A new Wisconsin lawsuit asks whether the Supreme Court’s reasoning in Chatrie v. United States impacts warrantless searches of aggregated license plate reader databases. Law enforcement agencies should distinguish immediate threats from broad historical searches of automated license plate readers. Strong policy safeguards, audits, and supervisory reviews help agencies keep a useful investigative tool from becoming an unrestricted movement-tracking system.
Automated license plate readers (ALPRs) are extraordinarily useful. They help officers find stolen vehicles, locate missing people, identify vehicles associated with violent crimes and develop leads that might otherwise take days of conventional police work.
But the current controversy is not really about whether a camera may read a license plate displayed on a public roadway. It is about what happens when thousands of cameras preserve those observations in a searchable database capable of reconstructing a vehicle’s movements across cities, states, and time. A new Wisconsin lawsuit puts that question squarely on the table.
Six Cameras, 3 Million Searches
On September 10, 2026, the Wisconsin Institute for Law & Liberty announced a lawsuit against Waukesha County and 11 municipalities challenging their use of Flock Safety’s aggregated ALPR database. The plaintiffs are not asking the court to remove the cameras or prohibit conventional ALPR use. They want warrantless access to the larger historical-location database declared unconstitutional.
The numbers alleged in the complaint explain the concern. Flock reportedly operates approximately 120,000 cameras used by more than 6,000 law enforcement agencies. According to the plaintiffs, Elm Grove officers searched data from their six local cameras approximately 250 times during June, July, and August. During the same period, outside agencies — many located in other states — reportedly queried Elm Grove’s camera data approximately 3 million times.
Those are allegations, not adjudicated facts. No court has found that any of the agencies violated the Fourth Amendment, and no merits ruling has happened. But the lawsuit identifies a constitutional question agencies should not dismiss as merely theoretical.
“Policy cannot make an unconstitutional search constitutional, but it can keep officers from casually turning a legitimate investigative tool into an unrestricted movement-tracking system.”
The extraordinary volume of out-of-area ALPR searches alleged in the Wisconsin lawsuit is not unique. Records released by the Weber County Sheriff’s Office in Utah show 10 county Flock cameras or associated networks appeared in more than 5.1 million searches between February 2022 and July 2026. According to an analysis by the Utah Civic Compact, 96.6% of those searches originated outside Utah; during the first seven months of 2026, the figure rose to 98.6%. Houston police alone conducted more than 423,000 searches during that seven-month period. These figures do not necessarily mean that outside officers deliberately targeted Weber County each time — a single, broad Flock query may automatically reach thousands of participating networks. But that is precisely the concern: Cameras acquired to serve a local community can become nodes in a nationwide system, repeatedly searched by agencies the collecting department does not supervise and cannot meaningfully audit.
A single camera records a car at a particular place and time. A nationwide network may be able to reveal where that car has been, where it frequently travels and which other vehicles commonly travel with it. The constitutional issue is whether aggregation changes the nature of the government’s conduct.
What Chatrie Held
The plaintiffs rely heavily on the Supreme Court’s 2026 decision in Chatrie v. United States. Police investigating a Virginia bank robbery obtained a geofence warrant directing Google to identify devices found within 150 meters of the bank around the time of the crime. The process eventually produced two hours of location information associated with Okello Chatrie.
When they acquired Chatrie’s Google Location History, the U.S. Supreme Court held, police conducted a Fourth Amendment search. Importantly, the Court rejected the argument that two hours of data was categorically too short of a period to receive constitutional protection. Highly precise location data can reveal sensitive associations and movements even over relatively limited time frames.
But Chatrie did not decide ALPR databases are unconstitutional. It did not involve license plates, vehicles, or observations made by cameras on public roads. Nor did the Court hold that every geofence warrant is invalid. Rather, the Court decided the threshold question: Obtaining Chatrie’s location information was a Fourth Amendment search.
Agencies defending ALPR technology have substantial arguments. A license plate is deliberately exposed to public view, and vehicles travel on public roads. ALPR data is generally less continuous than cellphone location data, and a plate identifies a vehicle, not necessarily its driver. A camera observing a vehicle passing through an intersection is doing electronically what an officer standing at that intersection could lawfully do.
The plaintiffs’ response is equally straightforward: No team of officers could stand at 120,000 locations, remember billions of observations and reconstruct a person’s interstate travel in seconds. The constitutional concern arises from the database’s aggregation, retention, geographic reach, and extraordinary ease of searching — not simply from the camera capturing the image.
That is the post-Chatrie question: When does a collection of individually lawful public observations become a constitutionally significant record of a person’s movements?
Not Every ALPR Use Is the Same
Courts should resist treating all ALPR use as one undifferentiated activity. An immediate hot sheet alert identifying a stolen car is considerably different from searching months of historical data to determine everywhere a vehicle has traveled. A query for a suspect vehicle seen near a homicide scene is different from conducting an open-ended nationwide search without a defined crime or investigative purpose.
Several characteristics may become important:
- The period covered by the search.
- The number and geographic distribution of cameras queried.
- Whether the search concerns a known vehicle or attempts to identify an unknown person.
- Whether the data reveals patterns, associations, or frequently visited locations.
- Whether the system supplies individual sightings or constructs a complete journey.
- Whether the information is historical or provides continuing, near-real-time tracking.
- Whether an outside agency can search local data without notice or approval.
The eventual constitutional rule may turn on some combination of these factors. It is unlikely to be as simple as “all ALPR searches require warrants” or “anything visible on a public road is fair game.”
Even if a database query constitutes a search, a warrant will not always be necessary. Exigent circumstances, consent, and other recognized exceptions remain available. An endangered child or fleeing violent offender presents a very different risk profile from a routine intelligence inquiry conducted weeks later.
Lexipol Policy Provides a Sound Starting Point
This is where policy matters. Policy cannot make an unconstitutional search constitutional, but it can keep officers from casually turning a legitimate investigative tool into an unrestricted movement-tracking system.
Lexipol’s ALPR policy framework offers excellent guidance. The Lexipol ALPR policy includes several especially valuable safeguards:
- A designated ALPR administrator.
- Individual login credentials and access records.
- System access limited to trained and authorized personnel.
- Use restricted to official law enforcement purposes.
- Independent verification of an alert before enforcement action.
- Audit trails recording queries, responses, sharing, and dissemination.
- Defined retention and deletion requirements.
- Written justification, a factual basis, and an associated case or incident number for outside-agency requests.
- Supervisory review before information is released.
- A warrant or exigent circumstances is required before using ALPR technology to monitor or track an individual.
Agencies should also consider requiring supervisory or legal review before extended historical, regional, or nationwide searches. The broader and more retrospective the inquiry, the more it begins to resemble the movement reconstruction that concerned the Supreme Court in Carpenter and Chatrie.
A “reason” field that accepts anything an officer types is not meaningful oversight. Neither is an audit log nobody reviews. Agencies should sample queries, verify them against reports and case numbers, investigate anomalies, and document corrective action.
Timely legal analysis on law enforcement-related cases: SUBSCRIBE NOW!
What to Watch
Although this lawsuit is still unfolding, agencies should not wait for an appellate court to tell them unlimited access was a mistake.
The strongest position is both operationally useful and constitutionally disciplined:
- Preserve immediate alerts and focused investigative searches.
- Impose greater controls as searches become broader or more historical.
- Require warrants when the inquiry amounts to prolonged movement tracking unless an exception applies.
- Maintain genuine audit and supervisory systems.
The camera may see only one car at one intersection. The constitutional problem begins when the database allows law enforcement to reconstruct a life.
- Blog Articles
