The Constitutional Question
The starting point for almost every legal challenge is Carpenter v. United States(2018), where the Supreme Court held that long-term cell-site location tracking requires a warrant because it reveals a detailed picture of someone's life. The open question since then is whether ALPR data — far less granular than continuous cell tracking, but increasingly dense and increasingly networked — eventually crosses that same line. Courts call this the "mosaic theory": enough small, individually-legal observations can add up to a search that requires a warrant. Confirmed
How Courts Have Ruled So Far
United States v. Martin (Virginia Federal District Court)
The court found that a warrantless ALPR database search used to identify an armed robbery suspect did not violate the Fourth Amendment — reasoning that three discrete images over 30 days weren't enough to reconstruct someone's full movements. Confirmed
Schmidt & Arrington v. City of Norfolk
The Institute for Justice argued Norfolk's 176-camera network formed an unconstitutional tracking dragnet. In January 2026, the judge dismissed the case — but explicitly warned that ALPR surveillance could eventually become intrusive enough to violate the Constitution as networks grow denser. The plaintiffs have appealed to the Fourth Circuit. Confirmed
Pettersson v. Flock Safety (San Francisco)
A class action alleging Flock systematically violated California's ALPR Privacy Act by letting federal and out-of-state agencies query California vehicle data — citing audits showing 1.6 million searches against SFPD's database and over a million against Los Altos's. Confirmed
California v. City of El Cajon
California's Attorney General sued El Cajon directly, alleging its police department shared ALPR data with over 100 out-of-state agencies — including states with strict abortion bans like Texas, Florida, and Georgia. Confirmed
State Laws — Moving Faster Than Federal
With no comprehensive federal ALPR law, states have become the primary venue for actual restriction:
- Washington (SB 6002, March 2026): 21-day retention cap, bans collection near clinics and places of worship, bans use for immigration or reproductive healthcare enforcement, requires a warrant for police to access private ALPR databases.
- Connecticut (Public Act 26-14, May 2026): 21-day retention cap, bans use targeting protected characteristics or immigration status, and creates a private right of action for citizens to sue violating officers.
- California (SB 34): Restricts sharing to California public agencies only — no out-of-state or federal sharing without a California court warrant.
- New Hampshire: Near-total ban on highway ALPR use outside critical infrastructure protection.
- Maine: 21-day statutory purge limit, law enforcement use only.
Confirmed The pattern: every one of these laws was passed after a documented violation became public, not proactively.
Congressional Oversight
In August 2025, Representatives Robert Garcia and Raja Krishnamoorthi opened a formal investigation into Flock Safety, demanding a full accounting of every National Lookup search containing terms like "abortion," "ICE," or "CBP," plus copies of any agreements with federal immigration agencies. Confirmed As of this writing, no comprehensive federal ALPR regulation has passed.
Flock's Contract Terms Got Less Favorable to Cities
In February 2026, Flock updated its standard contract terms in a way the ACLU found shifted legal power away from municipal customers: a perpetual worldwide license to use "anonymized" aggregated data even after a contract ends, expanded liability protections for the company, and a requirement that contract disputes go through private arbitration under Georgia law — making it harder for cities to simply walk away after a council vote. Confirmed
What You Can Actually Do
You can file a public records request for your local department's ALPR contract, audit logs, and data-sharing agreements — see Toolsfor how. If your state hasn't passed ALPR-specific legislation, model language already exists in Washington's and Connecticut's laws that advocacy groups have used as templates elsewhere.