Automatic license plate readers, or ALPRs, have spread across American roads. Mounted on poles, patrol cars and even private property, these systems snap images of passing vehicles and log plate numbers with time and location stamps. Agencies use them to spot stolen cars and wanted suspects in real time. Databases built by vendors such as Flock Safety now hold millions of records that officers can query for historical movements.
Andrew Wheeler, a criminologist who has worked with police departments on data projects, argues in a new post that searches of those historical records should require a warrant. He points to the growing density of cameras and the risk that broad access turns routine driving into a searchable log of personal activity. Andrew Wheeler’s blog.
Courts have reached different conclusions. In March 2026 the Fifth Circuit ruled in United States v. Porter that periodic ALPR hits on public roads did not trigger Fourth Amendment protections. The panel distinguished the snapshots from the continuous tracking in Carpenter v. United States, the Supreme Court cell-site case. Fifth Circuit opinion summary. Earlier state rulings, including Massachusetts’ Commonwealth v. McCarthy, left room for warrants when camera networks become dense enough to reconstruct detailed travel patterns.
Virginia provides the sharpest recent clash. A Norfolk trial judge suppressed ALPR evidence in Commonwealth v. Church because officers pulled historical data without a warrant. The Electronic Frontier Foundation, ACLU of Virginia and National Association of Criminal Defense Lawyers filed an amicus brief urging the Court of Appeals to keep the suppression. EFF amicus filing. In October 2025 the appellate court reversed, holding that pictures of plates on public streets did not amount to a search. Flock Safety statement on ruling.
Legislatures have moved faster than courts in some states. Colorado’s Senate Bill 26-070 passed a committee in February 2026. It would have forced officers to obtain a warrant for ALPR database queries more than 72 hours after a reported crime. Additional provisions limited out-of-state sharing and capped retention at 30 days unless an active case justified longer storage. Lawmakers withdrew the measure in May amid objections from law enforcement. Colorado Newsline coverage.
California’s ALPR Privacy Act has spawned a wave of civil suits. Plaintiffs claim parking operators and other private entities collected plate data without required privacy policies. At least four class actions target Flock installations and data-sharing practices. One complaint alleges the company routed California records to out-of-state agencies without proper safeguards. Class action complaint details.
LAPD paused new Flock deployments in July 2026 after an inspector general review flagged weak controls on data access. The department cited concerns that records could reach federal immigration enforcement despite local policies. Los Angeles Times report. Similar audits in other cities have uncovered queries for non-criminal purposes, including romantic surveillance and immigration checks.
Wheeler notes that simply deleting old records harms investigations and fails to stop abuse. He favors external audits of access logs and clear warrant standards once data volume crosses a threshold comparable to cell-phone tracking. Short-term queries for active alerts would remain unrestricted. His view aligns with Brennan Center recommendations from 2020 that historical searches of retained plate data should meet probable-cause requirements. Brennan Center report.
Congressional Research Service analysts summarized the split in a July 2025 overview. No federal appeals court has yet declared routine historical ALPR queries a search, yet several district judges and one circuit concurrence flagged risks if networks grow comprehensive. The plain-view doctrine still shields the initial camera capture on public roads. Database queries raise harder questions when millions of innocent movements become instantly retrievable. CRS In Focus.
Private vendors now operate the largest networks. Flock Safety cameras appear in dozens of cities, and the company markets real-time alerts plus historical search tools. Recent reporting shows configuration errors allowed unintended cross-agency queries in multiple jurisdictions. Police departments have responded by tightening internal policies and demanding daily audit reports from the vendor. ACLU analysis of vendor practices.
Advocates on both sides see momentum. Privacy groups push for statewide model bills that mirror the ACLU template released in early 2026. Law-enforcement organizations emphasize solved cases involving stolen vehicles and endangered persons. Data from 2025 shows billions of plate reads annually, the vast majority involving drivers with no connection to crime.
The doctrinal tension persists. Carpenter required warrants for long-term cell-site records because they painted an intimate portrait of daily life. ALPR systems currently produce sparser data points, yet camera density continues to rise. Fifth Circuit precedent treats the hits as discrete public observations. Virginia’s reversal and Colorado’s withdrawn bill illustrate how policy responses diverge by jurisdiction.
Future cases will test whether aggregated ALPR logs, when paired with other datasets, cross the Carpenter line. External oversight of query logs offers one practical safeguard in the meantime. Wheeler’s call for warrants on retrospective searches reflects growing recognition that once cameras blanket enough roads, location history becomes as revealing as phone records. Courts and legislatures will decide how strictly to cabin that capability.