EFF, ACLU Ask Ninth Circuit to Declare Reverse Location Warrants Unconstitutional
EFF and ACLU filed an amicus brief opposing reverse location warrants in the Ninth Circuit.
Why it matters: This case could reshape limits on law enforcement's ability to collect mass location data, impacting digital privacy and criminal procedure nationwide.
- The amicus brief challenges 'tower dump' warrants that collect location data for all devices at specific cell towers.
- One warrant collected data from 1,686 devices over six hours near two rural highway mile markers.
- The Center for Democracy & Technology and other groups also filed briefs criticizing the warrant as a general warrant violating the Fourth Amendment.
- This marks the first federal appeals court challenge to such warrants following Supreme Court rulings on geofence cases.
On November 3, 2026, the Electronic Frontier Foundation (EFF) and the American Civil Liberties Union (ACLU) filed a joint amicus brief in the Ninth Circuit Court of Appeals in the case United States v. Spurlock, challenging the constitutionality of so-called 'tower dump' or reverse location warrants. These warrants compel cellular providers to disclose location data for every device that connected to specific cell towers during defined time windows.
The warrant in this case required providers to turn over location information for all devices connecting to two rural highway mile markers over a six-hour period, leading to the collection of data on 1,686 devices. According to EFF Senior Staff Attorney Andrew Crocker, "These overbroad warrants require cellular providers to turn over location data about every phone in a given area at a given time." This broad scope results in substantial privacy intrusions on many innocent individuals.
Adding to the criticism, the Center for Democracy & Technology (CDT) and other privacy advocates also filed amicus briefs condemning the warrant. CDT Deputy Director Jake Laperruque stated, "The tower dump here was needlessly broad, pulling in over 1000 individuals over a span of hours, and collecting Fourth Amendment-protected data without particularity, narrowing mechanisms, or probable cause of wrongdoing for any of the individuals whose private location information was seized."
This case has drawn significant attention as it represents the first federal appeals court review of reverse location warrants following the Supreme Court's ruling on related geofence warrants. The outcome may set vital limits on law enforcement's ability to obtain bulk location data via cell towers, especially when such data encompasses many uninvolved people.
The EFF and ACLU argue for a categorical constitutional bar against such warrants, emphasizing the significant privacy and Fourth Amendment issues raised by mass, non-targeted collection. The Ninth Circuit's decision could influence similar cases nationwide and shape the balance between digital privacy and criminal investigations.
By the numbers:
- 1,686 devices — location data collected in the tower dump warrant
- 6 hours — time frame during which data was collected
- 2 rural highway mile markers — locations specified in the warrant
What's next: The Ninth Circuit's ruling in United States v. Spurlock will clarify the legality of reverse location warrants and may prompt further Supreme Court review.