Geofence and Keyword Warrants: What US Investigators Can and Can't Get in 2026
Reverse-location and reverse-keyword warrants are powerful and legally unsettled. A guide for US investigators: how the three-step geofence process works, the circuit split (Smith vs Chatrie), the Supreme Court case now pending, and why Google's move to on-device location has changed the game.
Reverse warrants flip the usual order of an investigation. Instead of naming a suspect and asking for their data, you describe an area and time (a geofence warrant) or a search term (a keyword warrant) and ask a provider who was there or who searched it. They can crack a case with no suspect. They are also among the most legally contested tools in US law enforcement right now, and an investigator who relies on one needs to understand exactly how unsettled the law is.
- Geofence (reverse-location): a three-step process, historically run against Google, returns anonymised devices in an area and time, which you then narrow and de-anonymise.
- The law is split: the Fifth Circuit held geofence warrants unconstitutional (Smith, Aug 2024); the Fourth Circuit found no Fourth Amendment search at all (Chatrie, 2024). The Supreme Court is deciding.
- Google has changed: location history (Maps Timeline) is moving to on-device storage, which has significantly reduced Google's ability to answer geofence warrants.
- Keyword warrants exist and are heavily challenged; no appellate court has settled their constitutionality.
How a geofence warrant works
The classic process runs in three steps:
- Step 1, anonymised list. The provider returns a de-identified list of devices whose location data falls inside the geographic and time bounds in the warrant, labelled only by anonymous device identifiers.
- Step 2, narrowing. Investigators review the anonymised data and select the devices of interest, sometimes requesting an expanded window around them to establish relevance.
- Step 3, identification. For the narrowed set, the provider discloses subscriber-identifying information. Only here do anonymous devices become named people.
The legal split investigators must know
This is the part that decides whether your evidence survives a suppression motion. The federal circuits disagree:
- Fifth Circuit, United States v. Smith (August 2024): held that geofence warrants are unconstitutional, calling them modern-day general warrants of the kind the Fourth Amendment was written to forbid. The court still admitted the evidence under the good-faith exception, but the constitutional holding stands in that circuit.
- Fourth Circuit, United States v. Chatrie (2024): reached the opposite conclusion, finding that obtaining a short window of Google location history was not a Fourth Amendment search at all under the third-party doctrine. An en banc rehearing split evenly.
Because the circuits conflict, the Supreme Court granted review and heard argument in 2026, with a decision pending. Until it rules, the constitutionality of geofence warrants depends on your jurisdiction. Document your particularity and minimisation carefully, and expect a challenge.
Why the data may not be there anymore
Even where geofence warrants are permitted, the well is drying up. Google announced in late 2023 that Maps Timeline location history would migrate to on-device storage, rolling out through 2024. Once a user's data is on-device, Google no longer holds it on its servers and cannot answer a geofence warrant for that user. The practical effect is that historical-location dragnets against Google have been significantly reduced. Increasingly the location evidence lives on the seized handset, not in a provider's cloud.
Keyword (reverse-search) warrants
The keyword warrant asks a provider to identify every account that searched a specified term in a window. It has solved cases, and it draws the same general-warrant objections as geofence. As of 2026 no federal appellate court has definitively ruled keyword warrants constitutional or not, and civil-liberties groups challenge them routinely. Treat them as high-risk and narrowly scoped.
Practical guidance
- Check your circuit. The same warrant that is fine in one circuit may be void in another until the Supreme Court resolves the split.
- Particularise. Tight geographic and temporal bounds, a clear nexus, and a minimisation protocol are your best defence against a general-warrant attack.
- Expect on-device evidence. With Google's shift, plan to obtain location data from the device under a warrant, not from the provider. See CDR, IPDR and tower dumps for the network-side records that remain available.
Frequently asked questions
Are geofence warrants legal in the US? It depends on the circuit and may soon depend on a pending Supreme Court decision. The Fifth Circuit holds them unconstitutional; the Fourth Circuit found no search occurred. The law is unsettled.
Can Google still answer a geofence warrant? Less and less. As location history moves to on-device storage, Google often no longer holds the data to produce.
What is a keyword warrant? A request for the identities of accounts that searched a specific term. It is legally contested and not settled by any appellate court.