EPIC Tells Supreme Court that Geofence Searches Need a Warrant with Particularized Probable Cause

This week, EPIC filed an amicus brief on behalf of 14 leading law & technology and Fourth Amendment scholars in the Supreme Court case Chatrie v. United States explaining why the Court should rule that geofence searches require a warrant, and why the warrant issued in this case (and many others involving geofence searches) was unconstitutional.

Geofence searches are a relatively new and concerning investigative technique in which government officers require companies such as Google to tell them everyone whose device was within a certain area (a geofence) within a certain timeframe. These companies’ vast collections of users’ location history data provide a rich target for investigators. Geofence searches raise serious privacy and Fourth Amendment questions, and federal courts of appeals have split on the issue of whether the searches (and warrants permitting them) are constitutional.

This case is set to be a landmark trial. The Supreme Court has not taken up a Fourth Amendment case since it decided Carpenter v. United States in 2018—another case involving the location data that companies create and store about individuals through their cell phones. In that case, the Court ruled that investigators needed a warrant to obtain historical records of people’s movements created by cell phone pings to cell towers. Geofence warrants are similar in many ways, but also present unique privacy challenges, especially in an era of increased surveillance of protestors and journalists, among other important speakers.

EPIC’s brief makes three main arguments. First, it argues that the Court should use the analysis set forth in Carpenter to rule that geofence searches require a warrant under the Fourth Amendment. Carpenter established a useful, workable test for Fourth Amendment protections in the Digital Age, and each of the factors discussed in that case, when applied to geofence searches, militate in favor of Fourth Amendment protections.

Second, the brief urges the Court to rule that users do not waive their Fourth Amendment rights to location data merely because they agree to provide it to companies such as Google. Users are often asked to provide location tracking permissions while setting up their phone and apps. A barrage of forced permission screens require users to click “accept” or “deny” before using an app. These screens omit important information about the consequences of accepting tracking, and they use dark patterns to manipulate users into accepting tracking. The privacy policies they link to are longer and more technical than most people have the time or training to understand. Furthermore, many important apps are designed not to work properly without tracking permissions, whether or not they are really necessary for the app to function. And many users, even if they understand what they are accepting to, do not imagine that granting permissions to companies like Google means that they are waiving their Fourth Amendment rights. The brief illustrates these points using actual record evidence from Chatrie’s case.

Third, the brief argues that the geofence warrant used in this case, and many others, was unconstitutional because it lacked particularized probable cause at each of its steps. The warrant “failed to describe target devices with particularity and gave unlimited discretion to officers executing the warrant to obtain precise location data about any device that happened to be in the vicinity of the crime they were investigating within a one-hour period.”

The Supreme Court will hear oral argument in the case on Monday, April 27, 2026.

EPIC regularly advocates for privacy protections from government surveillance and consumer privacy laws that would reduce the privacy threat posed by techniques such as geofence warrants.