International law firm McDermott Will & Schulte represented the Center for Democracy and Technology and the Rutherford Institute in filing two Supreme Court amicus briefs in United States v. Chatrie, a case carrying significant weight for Fourth Amendment privacy protections and location history data.

“The Center for Democracy & Technology was proud to submit a brief in the Chatrie case, which could have a huge impact on Fourth Amendment protections for location privacy and have a pivotal impact in how ‘reverse warrants’ for sensitive digital data are treated,” said Jake Laperruque, Deputy Director for the Security and Surveillance Project at the Center for Democracy and Technology. “We’re grateful to McDermott Will & Schulte for its invaluable assistance in helping us highlight the importance of protecting privacy rights in the digital age.”

The briefs urge the Supreme Court to overturn a Fourth Circuit decision in United States v. Chatrie, which, if left intact, would erode Fourth Amendment protections in a person’s location history data. The Supreme Court’s decision will determine whether reverse dragnet warrants are permissible under the Fourth Amendment. These warrants would allow the government to request location history data from all people in an area of a crime without particularity or probable cause.

Demonstrating a unified and powerful stance to protect privacy rights in location data for all Americans, the Center for Democracy and Technology, joined by the Surveillance Technology Oversight Project, the Brennan Center for Justice, and Defending Rights & Dissent, submitted a joint brief, with the Rutherford Institute submitting a separate complimentary brief, requesting the Fourth Circuit decision be overturned and the geofence warrant at issue found unconstitutional.

“If a warrant can be obtained to search the movements of everyone in a given area based on the likely fact that someone who was in that area probably has a cell phone, the government effectively has carte blanche to demand site-tracking information on anyone at any time,” said the Rutherford Institute in its brief. “The intrusive power of government surveillance may be applied to any unfortunate person who happens to be in the wrong place at the wrong time carrying a cell phone. Such intrusion based on a general warrant is not only plainly unconstitutional, but a threat to the fundamental right to privacy.”

“By compelling the disclosure of location data for every device within a defined area, geofence warrants resemble the very general warrants the Fourth Amendment was designed to prohibit,” echoed the Center for Democracy and Technology in its brief. “If upheld without meaningful limits, geofence warrants could normalize suspicionless digital dragnets as a routine investigative tool.”

Digital location history data can be some of the most sweeping, granular, and comprehensive information about a person. By creating a journal of one’s movements, it can reveal the “privacies of life” including “familial, political, professional, religious, and sexual associations.” In this case, law enforcement requested a geofence warrant requesting anonymized user data of every person who was in a 150-meter radius of the crime for a one-hour period. Then, without an additional warrant, the government demanded location information for a period of time before and after the set duration of the geofence, without any limit to its geographic bounds. Finally, the government demanded and received deanonymized information for multiple devices.

Geofence warrants are effectively “digital dragnets” that permit searches of broad swaths of private individuals’ movements without the constitutionally mandated particularization of place or person. The amicus briefs emphasize that the Fourth Amendment’s protections must adapt to technologies that can reveal intimate details about individuals’ associations, movements, and activities. Geofence warrants lack the required constitutional particularity because they authorize searches of every account meeting a broad set of criteria without requiring individualized probable cause.

Permitting such warrants would enable pervasive surveillance without meaningful judicial oversight – not only of criminal suspects, but of innocent bystanders who happen to be in the area at a particular time.

Relying on the reasoning of Carpenter v. United States, detailed location data reveals intimate information about a person’s movements, associations, and daily life, warranting robust constitutional protection even when held by a third party. Additionally, indiscriminate collection of location data raises First Amendment concerns, risking exposure of individuals’ attendance at religious services, political gatherings, protests, or other expressive and associational activities, thereby chilling the exercise of free speech and assembly. These arguments frame geofence warrants as a constitutional inflection point for how courts reconcile modern digital surveillance practices with foundational protections against government overreach.

A ruling invalidating geofence warrants on constitutional grounds could signal heightened Fourth Amendment protection for digital data, reinforcing privacy expectations for users of location-based services and influencing how technology companies respond to law enforcement demands. Conversely, if the Court affirms their use, it may embolden broader government access to detailed digital records under warrant authority. This has potential to reshape investigative practices and opens the door to other forms of reverse-search warrants, including keyword queries, AI chatbot prompt disclosures, and IP address searches – tools that seek information about individuals based on online activity rather than individualized suspicion. The decision may also clarify the continued scope of the third-party doctrine in an era where vast amounts of sensor-derived and cloud-stored personal data are routinely collected, with implications extending well beyond geofence warrants. A definitive ruling could therefore reshape digital privacy law for years to come, either reinforcing robust constitutional limits on digital surveillance or endorsing expanded law enforcement authority in the digital sphere.

Oral arguments in Chatrie are scheduled for April 27, 2026, with observers monitoring the Justices’ approach to reasonable expectations of privacy in digital records, the application of traditional Fourth Amendment principles to evolving technologies, and the continued vitality of the particularity requirement.

The McDermott team representing Center for Democracy and Technology includes Alex Southwell, Katelyn Ringrose, Tyler Henry, Sagar Ravi, and Jon Hawk.

The McDermott team representing Rutherford Institute includes Ethan Townsend and Maura Cremin.

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