This post was co-written by Andi Cao, an EFF legal intern.
Automated license plate readers (ALPRs) are mass surveillance. They photograph every passing car and log where and when it was captured, building a searchable record of where nearly everyone drives. Cities should not buy them, and cities that already have them should shut them down.
Where these systems still operate, courts and state legislatures must reduce their harms by (among other things) requiring police to get a warrant before searching stored ALPR data. A warrant requirement would not make mass surveillance acceptable, but it would require police to justify a search to a judge before accessing records of people’s movements. Without this independent judicial check on police power, officers have been searching this data for improper reasons (many exposed by EFF) that violate our fundamental rights.
A warrant requires a judge to find probable cause and specificity—many warrantless police searches of ALPR data lack both. Officers have searched this data to profile Romani people, monitor protesters, investigate an abortion, find immigrants for deportation, track a man who complained about a deputy, stalk romantic partners, and even for no stated reason beyond “LMAO.” A warrant requirement would force law enforcement to justify these searches before accessing sensitive location records, not leave the people they target to discover and challenge the abuse after the harm is done.
What a Warrant Requires
Warrants are a check on police power. Before officers can search a person or their property, the Fourth Amendment requires them to convince a neutral judge, under oath, that probable cause exists, meaning a fair probability the search will turn up evidence of a crime. The warrant must also describe with particularity what will be searched, so police cannot go on a fishing expedition. Critically, the officer who wants to search is not the person who decides whether the search is justified.
That is why warrants are required for so many kinds of police surveillance. For example, police generally need a warrant to wiretap phone calls, to search the contents of a cell phone, and to obtain historical cell phone location records.
Stored ALPR data reveals sensitive information about the private details of our lives: where we go, when, and with whom. That’s why we believe police searches of stored ALPR data should also require a warrant. Earlier this month, a federal judge in Oklahoma agreed.
What Goes Wrong Without a Warrant: San Jose, California
San Jose demonstrates the harmful consequences of letting law enforcement search stored ALPR data without a warrant. EFF and the ACLU of Northern California represent SIREN and CAIR-California in a lawsuit challenging this practice.
The first problem is the sheer number of times that SJPD officers search stored ALPR data: 261,711 times between June 5, 2024, and June 17, 2025, about 692 searches a day. That scale is the result of having no warrant requirement, which would greatly reduce this kind of casual police surveillance.
Inevitably, officers abuse this unchecked power. In September, San Jose’s police chief disclosed an example from five months earlier: the department had fired an officer who used its ALPR system to track a woman who had accused his cousin of domestic violence, and then shared her location information with his cousin. The abusive search of stored ALPR data came to light only after the woman told police that her alleged assailant had implied he was tracking her. A warrant requirement would have prevented this.
Of course, similar problems appear nationwide. For each example below, consider how things could have turned out differently if the officer had to put the reason for the search in a sworn warrant application and handed it to a judge.
Racial profiling of Romani people
More than 80 law enforcement agencies searched the Flock network using terms that unfairly stereotype Romani people, often without mentioning any crime. For example, the Grand Prairie (Texas) Police Department searched for “g*psy” six times using a Flock feature that identifies vehicles traveling together, in effect targeting a whole community without naming a crime.
No judge should sign that warrant. Ethnicity is not evidence of a crime, and a search aimed at an entire ethnic group is the opposite of particular: it targets people for who they are, not evidence that they committed a crime.
Surveillance of protesters
EFF found that more than 50 agencies ran hundreds of protest-related searches of ALPR data in 2025. For example, the Tempe (Arizona) Police Department ran three searches tied to the No Kings protest across 425 networks, with no identified crime.
This lacks probable cause and targets activity that is protected by the First Amendment.
Investigating an abortion
In 2025, a Texas sheriff’s office searched more than 83,000 Flock cameras, including cameras in Washington and Illinois, where abortion is legal, listing the reason as “had an abortion, search for female.” Records later obtained by EFF show deputies had opened a “death investigation” after the woman’s partner, who was later charged in connection with assaulting her, reported her self-managed abortion.
In a state where abortion is legal, a judge would not grant a warrant for a search like this.
Finding immigrants for deportation
San Francisco police let out-of-state agencies search the city’s ALPR data (which itself violates California law), and at least 19 of those searches were marked as related to ICE (though San Francisco is a sanctuary city). This problem is widespread. One investigation found more than 4,000 cases in which police departments around the country searched stored ALPR data on behalf of federal law enforcement, including for immigration investigations. Some agencies even connect their ALPR systems to an “Immigration Violator” hotlist populated by ICE, which includes plates tied to administrative warrants issued by ICE agents without any judge involved.
Here too, a judge in a state where police may not help enforce immigration law would not issue a warrant for these searches.
Retaliation against a critic
In May 2025, Navy veteran Napoleon Jones lawfully recorded a police traffic stop of another person in Sussex, Wisconsin. Jones alleges that a Waukesha County deputy retaliated by stopping and arresting him. He was released five hours later without citations or charges, and the deputy’s supervisor concluded the stop was illegal. Jones filed a complaint against the deputy the next day.
In the weeks that followed, officers reportedly ran more than 100 Flock searches against Jones, including some run by the deputy he had complained about. Deputies testified that a lieutenant ordered the searches in connection with Jones’s complaint.
No judge should authorize tracking a man for criticizing the police.
Stalking romantic partners
The Institute for Justice (IJ) has documented dozens of cases in which officers allegedly used ALPRs to track current, potential, and former romantic partners. For example, a Lufkin, Texas, officer was indicted on 100 felony counts after allegedly searching for his ex-girlfriend and people she knew more than 10,000 times. Likewise, a Milwaukee officer allegedly tracked a woman he was dating and her ex nearly 180 times over two months. IJ found that most of these cases surfaced only after victims reported the officer.
We hope that no officer would write “tracking the location of my ex-girlfriend” on a warrant application, and even if they did so, a judge would not authorize such a search.
Searches for “LMAO”
Sometimes officers do not even provide a real reason to search stored ALPR data. EFF found officers logging search reasons such as “LOL,” “LMAO,” “idk,” and random keyboard mashing. These entries are supposed to document why a search complies with an agency’s own use policies. A Goshen (Indiana) Police Department officer searched 6,474 networks, representing data from 82,413 cameras, with “idk” as the reason.
An officer who asked a judge for a warrant to track someone for “LMAO” would be laughed out of the courtroom.
The Solution
The best way to eliminate these abusive searches is to end ALPR mass surveillance. Where these systems remain, however, courts and state legislatures must require police to get a warrant before searching stored ALPR data. Warrants are the time-tested way to put an independent judicial check on police use of a dangerous surveillance technology. Officers must establish probable cause and specifically describe the proposed search before accessing the data, while existing exceptions for genuine emergencies still apply.
These protections must also cover real-time tracking. An ALPR “hotlist” is a list of license plates that trigger an alert when a camera spots a matching plate. Officers can stalk potential romantic partners by putting them on a hotlist, as a Florida deputy allegedly did with a woman he met on the set of a TV show. Thus, state legislators should require officers to get a warrant before putting a person on an ALPR hotlist (as well as a warrant to search stored ALPR data).