A geofence warrant (also called a reverse-location warrant) is a legal demand requiring a service provider to identify all users whose location data placed them within a specified geographic area during a defined time window. Most consequentially served on Google for its Sensorvault location-history database. Pioneered in US criminal investigations from 2017, with growing controversy through 2024 federal-circuit splits and ongoing Supreme Court attention to the reverse-search structure that defies traditional warrant particularity.
What it means in practice
The mechanic of a geofence warrant: the investigator defines a geographic area (a building, a street block, a neighborhood) and a time window; serves the warrant on Google requesting all device IDs whose Location History showed presence within the area during the window; receives an anonymized list of device IDs; narrows the list through follow-up investigation; serves a deanonymization warrant for the specific subscribers tied to the surviving device IDs. The structural concern is the reverse-search architecture: traditional warrants name a specific suspect, then seek their data; geofence warrants name no suspect, then identify all candidates from a location set, treating presence-at-location as the basis for individualized suspicion. The 2024-25 federal-circuit splits (Fifth Circuit in Smith v US 2024 finding geofence warrants unconstitutional; other circuits sustaining the practice) signal Supreme Court attention is likely.
Who it affects, and how
Operationally relevant for: anyone whose Google account has Location History enabled and who was physically present in any location that becomes the subject of an investigation; the inclusion in the candidate set is automatic and the deanonymization risk is significant if the location-and-time match the investigator’s search. Use cases that have driven controversy: protest investigations (post-2020 BLM-related geofence warrants, January 6 investigation, environmental and other protest-context warrants), property-crime investigations where the bulk inclusion of bystanders has produced wrongful-arrest cases, and the broader category of any high-profile event where investigators seek to identify all participants. Google’s 2024 announcement that it would migrate Location History to on-device storage (no longer accessible to Google or to geofence warrants) was the structural response to the geofence-warrant problem.
What you can change today
Three structural defenses. First, audit and disable Google Location History (Google Account, Data and Privacy, Web and App Activity, Location History, off; delete prior history). The 2024 Google migration to on-device storage means new Location History is no longer accessible to geofence warrants for users on the new architecture, but disabling entirely is the cleanest position. Second, audit and disable equivalent location-history features on other services: Apple Significant Locations (Settings, Privacy and Security, Location Services, System Services, Significant Locations, off and clear), Maps and navigation app history, ride-share location history. Third, for protest and other sensitive presence contexts: leave the phone home or carry a burner that is not associated with your identity; the data that does not exist is the data that cannot be returned in any geofence warrant.