The Fourth Amendment protects people against unreasonable government searches and seizures.
For most of American history, following somebody around required people, vehicles, fuel, time and patience.
Technology changes that equation.
A computer can remember observations humans would not have had the resources to collect, then search, compare and connect them later.
That creates an important constitutional question:
At what point does observation in public become something much more invasive because government can collect and search it at enormous scale?
First, an important disclaimer.
DeFlock Metro Detroit is a civic advocacy group. This page is educational information, not legal advice.
And we are not going to tell you the United States Supreme Court has already declared Flock cameras unconstitutional.
It has not.
ALPR-specific cases have reached different results depending on the facts. Other major digital-location cases establish principles that make the larger surveillance question increasingly important.
United States v. Jones
Long-term tracking changes the privacy question.
In United States v. Jones (2012), police attached a GPS tracking device to a vehicle and monitored its movements for 28 days.
The Supreme Court held that the government conducted a Fourth Amendment search. The majority relied heavily on the physical act of attaching the tracker.
Separate opinions also raised a broader concern that has become important to modern surveillance law: prolonged automated monitoring can reveal far more than ordinary observation.
Justice Sotomayor discussed how GPS monitoring can create a precise, comprehensive record capable of revealing familial, political, professional, religious and other associations.
Flock cameras are not GPS trackers. The relevance is the broader concern about cheap, automated, persistent movement tracking.
Carpenter v. United States
Detailed historical location information can deserve constitutional protection.
In Carpenter v. United States (2018), police obtained historical cell-site location information showing where Timothy Carpenter’s phone had been located over an extended period.
The Supreme Court held that obtaining the historical location information at issue was a Fourth Amendment search and generally required a warrant.
The Court recognized that detailed location records can provide an extraordinarily revealing picture of a person’s life.
Carpenter was not an ALPR case.
Its importance is the principle that aggregated digital location data can become constitutionally significant even when individual movements occurred outside the home.
Read Carpenter v. United States
Chatrie v. United States
In 2026, the Supreme Court again protected digital location information.
In Chatrie v. United States, decided June 29, 2026, police investigating a bank robbery used a geofence process involving Google Location History information.
The Supreme Court held that government acquisition of the cell-phone location information at issue constituted a Fourth Amendment search.
Chatrie involved cell-phone location data, not license plate readers.
Phones can reveal location in ways ALPR cameras cannot.
But the decision reinforces an important principle: digital location information does not become constitutionally insignificant merely because a technology company possesses it or because the government requests only a comparatively limited slice of it.
The Court left other questions about the particular warrant, including reasonableness questions tied to probable cause and particularity, for further proceedings.
Leaders of a Beautiful Struggle v. Baltimore Police Department
Public movement can become constitutionally different when government reconstructs the whole picture.
Baltimore operated an aerial surveillance program that repeatedly photographed large portions of the city.
The images were not detailed enough to identify faces, but investigators could work backward through stored imagery to reconstruct movement.
In Leaders of a Beautiful Struggle v. Baltimore Police Department (4th Cir. 2021), the en banc Fourth Circuit held that accessing the accumulated data was a Fourth Amendment search and that the warrantless program violated the Fourth Amendment.
The important idea was not that one image was private.
It was what investigators could learn from the whole of a person’s movements.
Read the Fourth Circuit opinion
This is sometimes called the mosaic problem.
Imagine hundreds of little tiles.
One tile tells you almost nothing.
Put enough together and an image appears.
Location surveillance can work the same way.
One vehicle observation may be meaningless.
Repeated observations around home, work, medical care, relationships, organizations and routines can produce a picture no individual observation reveals.
That is the constitutional concern.
Courts have considered ALPRs specifically.
This is where we have to be especially honest.
ALPR cases do not all point in one direction.
The details matter.
Commonwealth v. McCarthy
Four cameras were not enough. A larger network might be.
In Commonwealth v. McCarthy (Mass. 2020), Massachusetts’ highest court considered police use of four ALPR cameras located at the two bridges leading onto Cape Cod.
The court concluded that the particular deployment did not create a sufficiently detailed mosaic of location information to invade a reasonable expectation of privacy.
So the defendant lost the suppression argument.
But the court expressly recognized that widespread ALPR use could implicate constitutional protections.
The answer was essentially:
Not enough surveillance here.
Not:
ALPR surveillance can never raise constitutional concerns.
Commonwealth v. Church
In Commonwealth v. Church (Va. Ct. App. 2025), police used Norfolk’s Flock system in an investigation and the challenged database use produced a limited set of observations covering a short portion of the defendant’s route.
The Virginia Court of Appeals held that the particular use did not require a warrant, emphasizing the limited nature of the observations and distinguishing the situation from the comprehensive histories at issue in cases such as Carpenter.
That is important counterauthority.
It also illustrates how fact dependent these cases can be.
Robinson v. Commonwealth
In Robinson v. Commonwealth (Va. Ct. App. 2026), the Virginia Court of Appeals again rejected a Fourth Amendment challenge involving Norfolk’s Flock system.
The court described Norfolk’s network as 172 cameras capturing still images and exterior vehicle information, with records retained for 30 days. It held that the search at issue did not create the kind of comprehensive chronicle described in Carpenter.
Importantly, the court emphasized that analysis of new surveillance technology is fact based and declined to speculate about when a future Flock deployment might become comprehensive enough to create a reasonable expectation of privacy.
United States v. Porter
The Fifth Circuit rejected a challenge to the limited system used in that case.
In United States v. Porter (5th Cir. Mar. 17, 2026), an officer used an alert and records from a system with no more than ten cameras in Gautier, Mississippi. The Fifth Circuit held that this particular use did not invade a reasonable expectation of privacy and was not a Fourth Amendment search.
The court emphasized that the system produced periodic observations only when a vehicle passed one of those camera locations. It considered that record much less comprehensive and precise than the cell-phone and geofence data addressed in other location cases.
Porter is important counterauthority. It is binding in the Fifth Circuit, not Michigan’s Sixth Circuit, and it does not establish that every larger, denser or differently used ALPR network is constitutionally identical to the ten-camera system the court analyzed.
Read the Fifth Circuit opinion in United States v. Porter
Schmidt v. City of Norfolk
A major civil challenge is now on appeal.
Schmidt v. City of Norfolk directly challenged Norfolk’s Flock deployment as unconstitutional dragnet surveillance.
The federal district court initially allowed the lawsuit to proceed past the motion-to-dismiss stage. On January 27, 2026, however, the district court later granted summary judgment to the defendants and denied the plaintiffs’ summary-judgment motion.
That is an important development and should not be described as though the plaintiffs already won.
The constitutional challenge has continued in the Fourth Circuit Court of Appeals. As of our latest review, civil-liberties groups have filed appellate briefing arguing that the district court should be reversed.
So the correct status is:
district court judgment for Norfolk; appellate challenge ongoing.
Read the district court’s January 2026 opinion
Track the Fourth Circuit appeal, No. 26-1227 ↗
United States v. Kyle
One federal judge suppressed evidence from a warrantless historical ALPR search.
On October 1, 2026, a federal district judge in the Northern District of Oklahoma granted a motion to suppress in United States v. Kyle, No. 4:26-cr-00189-SEH.
The officer had access to Flock and VehicleManager records covering at least 30 days and many states. The opinion says he queried a California plate when all he initially knew was that the vehicle had an out-of-state plate, then used the resulting travel history as part of the investigation.
The court held that the query was a Fourth Amendment search and, on the facts before it, an unconstitutional warrantless search. The opinion described the network as approaching “indiscriminate mass surveillance” and distinguished older cases involving narrower technology or far fewer observations.
Read the October 1 opinion and order ↗
Washington Post explanation and response from Flock ↗
The limits matter:
- this is one federal trial-court ruling, not a United States Supreme Court decision;
- it does not bind courts in Michigan’s Sixth Circuit;
- Flock was not a party to the case;
- the vendor said it expected an appeal;
- and other courts, including the Fifth Circuit in Porter, have reached different conclusions on narrower facts.
The ruling is still important because it analyzed a networked historical search as a tracking system, not merely a single camera observing a visible plate.
What about Michigan?
Metro Detroit sits within the federal Sixth Circuit.
Carpenter itself came from the Sixth Circuit before the Supreme Court reversed the lower court’s location-data ruling.
As of this site’s current legal review, we have not identified a controlling Sixth Circuit decision categorically resolving whether a modern, large-scale networked Flock database itself constitutes a Fourth Amendment search.
That means we should not pretend Metro Detroit already has a binding appellate answer specifically addressing today’s Flock network.
The question is bigger than whether a plate is visible.
A common argument says:
Your license plate is visible to anyone standing on the street, so you have no privacy interest in it.
That identifies only part of the problem.
Yes, plates and vehicle exteriors are publicly visible.
The concern is whether technology lets government do something qualitatively different:
- record enormous numbers of observations;
- retain them;
- search them later;
- connect observations across locations;
- identify patterns;
- compare vehicles;
- and reconstruct movement without deploying officers to follow the person.
Practical impossibility used to protect privacy.
Imagine reproducing a regional ALPR network using human beings.
Place observers at every monitored road around the clock.
Have them write down every vehicle, time, direction, location and identifying characteristic.
Store every notebook.
Index it all.
Then let an investigator instantly ask where a vehicle appeared during the last month.
That would require enormous resources.
Automation removes much of that practical barrier.
That difference matters.
Thirty days can still reveal a lot.
Even where a system uses a 30-day retention period, think about your own previous month.
Work. Home. Medical care. Friends. School. Worship. Meetings. Relationships. Routines.
The relevant question is not whether 30 days is shorter than forever.
It is what government can learn during those 30 days.
A network can matter more than one city’s cameras.
A municipality might operate twenty cameras but have access to information gathered elsewhere through sharing arrangements.
Constitutional analysis may therefore depend on more than the number of devices the city owns.
The meaningful question can be:
How much location information can users actually search?
Artificial intelligence broadens the question.
Modern systems can increasingly search by vehicle characteristics, natural-language descriptions and pattern relationships rather than only a known plate.
Again, capability does not prove every feature is locally enabled.
But constitutional analysis should consider the actual system being used, not a twenty-year-old mental model of plate recognition.
What factors may matter?
No court has given one universal mathematical threshold.
But the cases suggest that facts such as these can matter:
- geographic coverage;
- camera density;
- retention time;
- outside network access;
- search capability;
- aggregation;
- association analysis;
- integration with other sources;
- and the degree of automation.
The more comprehensive those capabilities become, the weaker the analogy to one officer noticing one car becomes.
What makes a constitutional claim weaker?
Challenges may be weaker where the government uses a single observation, a handful of records, a short time period, limited geographic coverage and publicly visible exterior vehicle information closely tied to a specific investigation.
Recent courts rejecting ALPR challenges have emphasized facts like those.
That is why we do not say every ALPR observation automatically violates the Fourth Amendment.
What about warrants?
A warrant requirement could reduce some constitutional concerns.
It would not resolve our policy objection.
Even if a warrant were required for certain historical searches, the underlying database would still have been created on ordinary people first.
Our campaign’s end goal remains removal and nonrenewal.
Constitutional does not necessarily mean wise.
Suppose a court rules that a particular ALPR use is constitutional.
That answers one legal question.
It does not answer whether the city should buy it, whether the system is worth the money, whether the abuse risk is acceptable or whether a less invasive approach could achieve the same objective.
A city can respect privacy beyond the constitutional minimum.
Our argument does not depend on winning the constitutional question.
We believe large automated location-surveillance networks raise serious Fourth Amendment concerns.
There is significant legal reasoning supporting that concern.
There is also ALPR-specific authority rejecting challenges on narrower facts.
We can show both.
Because our policy argument is broader:
The Constitution is the floor of the debate. It does not have to be the ceiling of our expectations for privacy.
Last legal review: October 20, 2026. Surveillance law develops quickly. We re-check the cited cases and case status when major decisions occur or before relying on this page for a current legal claim.