License-Plate Cameras Track People Without Warrants

AI-enhanced automated license plate reader (ALPR) systems go beyond simple OCR. A Department of Homeland Security market survey (June 2025), cited by the Boston Bar Journal (Winter 2026), notes that modern ALPR systems can read much more than plates: they can detect dents, search for specific bumper stickers, process specialty tags, and recognize rideshare logos. Private vendors such as Flock Safety, Motorola Solutions, and PlateSmart supply cameras and databases to law enforcement; those databases can be shared automatically across departments nationwide, with no warrant required to conduct a search (Institute for Justice, August 2025).

Approximately 40% of US law enforcement agencies now use ALPR systems, per Boston Bar Journal research citing Police Chief Magazine (Oct. 2025). The Institute for Justice's Plate Privacy Project, launched in August 2025, documents concrete abuses: one police chief used cameras to track his ex-girlfriend and her new boyfriend more than 200 times; another officer allegedly tracked a woman he was dating nearly 180 times over two months before resigning and facing criminal charges (IJ, August 2025). ALPR data builds persistent movement histories over months or years, enabling retrospective tracking of individuals who have never been suspected of any crime.

Courts have not yet established a national standard. The Massachusetts SJC (2020) permitted warrantless access to four bridge-mounted cameras but noted that a more extensive network could trigger constitutional protection. The Fourth Circuit (2021) ruled that Baltimore's aerial surveillance program violated the Fourth Amendment because it enabled deducing the "whole of individuals' movements." In January 2026, a federal district court ruled in favor of the City of Norfolk's 170-camera Flock Safety network, distinguishing it from Carpenter v. United States on continuity and density grounds, though it acknowledged the constitutional calculus could shift as camera networks expand (Boston Bar Journal, Winter 2026). The EFF and ACLU of Northern California filed suit in November 2025 challenging ALPR use under the Fourth Amendment and California's right to privacy.

Washington state SB 6002, imposing new restrictions on ALPR deployments including Flock Safety systems, took effect March 30, 2026. The Institute for Justice is pursuing model legislation in state legislatures alongside its litigation campaign. A Congressional Research Service report (July 2025) provides a detailed federal-law background on ALPRs and Fourth Amendment doctrine.

ALPR surveillance is an active test case for how courts and legislatures apply privacy doctrine to AI-powered, continuously collecting systems. For practitioners deploying computer vision or location-linked AI in public contexts, the evolving legal landscape - active litigation, new state laws, and unresolved Fourth Amendment doctrine - is practical context for compliance and system-design decisions.