The Law
What the courts have actually held — including the parts that do not help us, and one Arizona decision that defeats an argument we would otherwise be tempted to make.
The hedging is the most useful thing on this page. If you tell a council that the Supreme Court has ruled license plate readers unconstitutional, the city attorney will correct you in public and everything else you say that night will be discounted. It has not. Saying precisely what these cases do and do not establish is what makes the argument survive contact.
The short version
No court has held that automated license plate readers are categorically unconstitutional. At least one published federal appellate decision has held that a small reader system is not a search. What courts have increasingly accepted is narrower and still useful: that assembling a detailed record of where a person has been can be a search, even when each observation happened in public and even when a company holds the data.
Our formulation, which we use deliberately and do not exceed:
Warrantless mass ALPR surveillance violates the principles and protections of the Fourth Amendment.
Principles and protections — not “is unconstitutional,” and not “the Supreme Court has ruled.” Those would be stronger sentences and we could not defend either.
- Supports our argument Decided — vacated and remanded to the Fourth Circuit
Chatrie v. United States
No. 25-112 (decided June 29, 2026) · Supreme Court of the United States
What it held Police conducted a search when they gained access to Google Location History data. A person has a reasonable expectation of privacy in records about their phone’s location, and police intrude on it when they demand that information — “even though for only a limited time, and from a third-party tech company.”
It removes two standard defences of warrantless location surveillance. On duration: “the sweep of the official invasion is not made less because the government, with the benefit of hindsight, can pinpoint exactly which few hours of movements it wants to review.” On the third-party doctrine: Location History is not “truly shared,” and a person is not to be treated as handing data to the government “just by doing the ordinary things cell-phone users do.”
Those are the two arguments a jurisdiction reaches for when it says its retention period is only thirty days, or that the data sits on a vendor’s servers rather than the city’s.
State this carefully: Four separate cautions, and all of them matter. First, the 6–3 is the judgment: Justice Kagan wrote for a five-justice majority, and Justice Gorsuch concurred in the judgment on a property theory instead — so never say “six justices held” about the privacy reasoning. Second, the decision does not mention automated license plate readers, license plates, or ALPRs anywhere in the opinion, concurrences, or dissents; the word “camera” appears exactly once, in the statement of facts, describing the credit union’s own security footage. Third, the Court did not overrule the older third-party cases and gave no rule for where the line now sits — applying either of its holdings to license plate readers is an argument we are making, not a holding we can cite. Fourth, the majority partly relied on Location History not being limited to public streets, which is precisely the distinction the industry now emphasises.
- Supports our argument Decided — suppression denied; the defendant lost
Commonwealth v. McCarthy
484 Mass. 493 (2020) · Supreme Judicial Court of Massachusetts
What it held “With enough cameras in enough locations, the historic location data from an ALPR system in Massachusetts would invade a reasonable expectation of privacy.” But on the facts — four readers on two bridges — “the limited use of ALPRs in this case does not constitute a search.”
This is the closest thing to an on-point appellate ruling in the country: the only state high-court decision to date squarely addressing whether ALPR use is a constitutional search.
The principle it establishes is that density and coverage matter. A handful of readers at fixed points is not a search; a network dense enough to reconstruct someone’s movements would be. That is exactly the argument to make about a modern deployment.
State this carefully: Say plainly that McCarthy lost. The court affirmed the denial of his motion to suppress. A page that quotes the helpful sentence without reporting the disposition is doing precisely what we accuse others of. It also binds only Massachusetts; elsewhere it is persuasive, not controlling.
- Supports our argument Decided
Carpenter v. United States
585 U.S. 296 (2018) · Supreme Court of the United States
What it held The government generally needs a warrant to obtain historical cell-site records chronicling a person’s past movements.
The foundational modern case: aggregating location data can be a search even when each data point was public or held by a company.
State this carefully: The Court called its decision narrow and expressly declined to extend it to conventional surveillance techniques or security cameras. It did not decide the ALPR question.
- Supports our argument Decided
United States v. Jones
565 U.S. 400 (2012) · Supreme Court of the United States
What it held Attaching a GPS tracker to a vehicle and monitoring its movements is a Fourth Amendment search.
The majority decided it on property grounds — the physical trespass of attaching the device.
The concurrences matter more here: five justices, across two opinions, indicated that long-term location monitoring can violate a reasonable expectation of privacy regardless of any trespass.
State this carefully: The holding rests on physical attachment. A camera on a pole attaches nothing to your car, so Jones does not transfer directly. Cite the concurrences’ reasoning, not the holding.
- Undecided Fully briefed. No ruling as of August 11, 2026.
Schmidt v. City of Norfolk
Fourth Circuit, No. 26-1227 · U.S. Court of Appeals for the Fourth Circuit
What it held An Institute for Justice challenge asking whether a city-wide network of license plate readers is a Fourth Amendment search.
The case to watch. It puts the question directly, and sits in the same circuit that now receives Chatrie on remand.
State this carefully: No ruling has issued. Predict nothing. This page will need updating the moment it does — check before relying on this entry.
- Cuts against us Decided
United States v. Porter
No. 25-60163 (5th Cir. Mar. 17, 2026) · U.S. Court of Appeals for the Fifth Circuit — published
What it held A license plate reader system of roughly ten cameras, producing only periodic hits on public roads, is not a Fourth Amendment search.
This is the most significant authority against our position, and it is a published federal appellate decision — binding in Louisiana, Mississippi and Texas.
We list it first among the adverse cases because it is the one a city attorney is most likely to have. Anyone arguing this in those three states needs to know it exists before they stand up.
State this carefully: Its reasoning turns on the modest scale of the system — roughly ten cameras giving periodic hits. That is the ground on which a dense modern network is distinguishable, and it is the same density logic McCarthy uses. But it is a real adverse holding, not a technicality.
- Cuts against us Decided — reversed the trial court and remanded
Commonwealth v. Church
Record No. 0737-25-1 (Oct. 14, 2025) — unpublished · Court of Appeals of Virginia
What it held “Because the Flock system simply took pictures of the license plate and Church’s vehicle as he drove it down public thoroughfares,” the trial court erred in ruling that a search warrant was required.
The trial court had ruled a warrant was necessary. This decision reversed that. EFF, NACDL and the ACLU appeared as amici supporting Church, and lost.
We publish it because leaving it out would be the kind of small dishonesty that costs an organisation everything the first time someone notices.
State this carefully: Two things make it weaker than it first appears. It is unpublished, so it is precedential nowhere. And it was decided eight months before Chatrie — its voluntary-exposure reasoning is now contestable on exactly the ground Chatrie rejected. That is how to address it honestly without conceding it.
- Cuts against us Decided — injunction dissolved; the police prevailed
Neal v. Fairfax County Police Department
295 Va. 334 (2018); 299 Va. 253 (2020) · Supreme Court of Virginia
What it held ALPR data is “personal information” under Virginia’s data practices statute, but the ALPR database is not an “information system” under that Act — so the statutory claim failed.
Included because it is squarely about ALPRs and because the plaintiff ultimately lost, which anyone citing state-court ALPR authority should know.
It is a statutory case, not a constitutional one — a useful reminder that the state-law route depends heavily on the exact wording of each state’s privacy statute.
Arizona: the argument that does not work, and the one that might
If you take one thing from this page in Arizona, take this. Article II, § 8 of the Arizona Constitution provides that no person “shall be disturbed in his private affairs, or his home invaded, without authority of law.” It is tempting to argue that this gives Arizonans broader protection than the Fourth Amendment. In this context, that argument loses.
In State v. Mixton, 250 Ariz. 282 (2021), the Arizona Supreme Court expressly declined to read Article II, § 8 more broadly than the Fourth Amendment for information conveyed to third parties, holding that IP addresses and subscriber data are not “private affairs” partly because they are voluntarily shared with third parties. It was a 4–3 decision, with Justice Bolick dissenting joined by the Chief Justice and Vice Chief Justice.
Arizona’s broader-than-federal protection has been confined largely to the home. Mixton is the case a city attorney will open with, and anyone arguing Article II, § 8 in Arizona without having read it will be embarrassed.
The narrower argument that remains available: Mixton’s third-party rationale rested on the idea that information shared with a company is not private. For location data specifically, that reasoning is now in tension with Chatrie, which held in 2026 that a person is not treated as sharing location data with the government just by using a phone normally. That is a real argument. It is also a much more modest one than “Arizona protects you more,” and it should be made in those terms.
We have found no ALPR lawsuit filed anywhere in Arizona. Arizona activity to date has been legislative and contractual rather than litigated — see the Decision Record.
The state constitutional front
Federal law is not the only route, and in several states it is not the most promising one. At least four ALPR suits have been filed since November 2025; three of them under state constitutions:
- SIREN & CAIR-CA v. City of San Jose Santa Clara County Superior Court · filed Nov. 19, 2025 · California Constitution · EFF and ACLU of Northern California
- Freeman & Steel v. Boulder Police Dept. (class action, 31 cameras) Boulder District Court · filed May 27, 2026 · Colorado Constitution · Andy McNulty
- Grimmett v. City of Wichita (~200 cameras) Sedgwick County District Court · filed approx. July 30, 2026 · Kansas Constitution Bill of Rights § 15 · Kansas Justice Institute
A fourth — an Institute for Justice class action against San Jose filed in federal court in April 2026 — pleads the federal Fourth Amendment rather than a state constitution, which is why we count it separately rather than inflating the number.
If you are working in another state, the first question is whether your constitution has its own privacy clause, and whether your supreme court has ever read it more broadly than the Fourth Amendment. Check that before building an argument on it — Arizona is a cautionary example of assuming the answer.
Why we publish the cases that hurt us
Porter, Church and Neal are on this page because they exist and they are not helpful to us. An organisation that publishes only supportive authority is doing advocacy dressed as research, and the first time a city attorney surfaces contrary authority we did not mention, everything else we said becomes suspect.
If we have characterised any of these incorrectly — particularly if you are a lawyer — please tell us. Getting the law wrong in public would damage this project more than any argument we could win by overstating it.
Nothing here is legal advice. It is a summary of published decisions for public education, current as of August 11, 2026. Cases move; check before relying on any of it. If you need advice about your own situation, consult a licensed attorney in your state.