The US Supreme Court delivered a 6-3 ruling today requiring law enforcement to obtain a search warrant under the Fourth Amendment before using geofence warrants to access location data [1, 2, 3, 4].

Geofence warrants allow police to compel companies like Google to provide location information for all users within a specified geographic area and time window. The court held that individuals have a reasonable expectation of privacy in their cell phone location history, including data collected by third parties like Google [1, 2, 3, 4].

Justice Elena Kagan wrote the majority opinion, stressing that Google often prompts users to enable location tracking without clearly disclosing how precise the data is or how it may be shared with law enforcement. She emphasized the need for constitutional privacy protections in such cases [1, 2, 4].

The case arose after police used a geofence warrant to track Okello Chatrie, suspected of robbing a Richmond, Virginia bank of $195,000. Chatrie had opted into Google's location history service, which recorded his movements every few minutes. He pleaded guilty and was sentenced to 12 years in prison [1, 2, 4].

Chatrie's lawyers argued the geofence warrant was too broad and violated the Fourth Amendment's safeguard against unreasonable search and seizure. The government claimed there was no reasonable expectation of privacy for location data collected in public or held by third parties like Google. The court rejected the government's argument, ruling that location history is constitutionally protected and requires a warrant for access [1, 2, 3, 4].

The ruling does not ban geofence warrants but requires that requests be supported by probable cause and narrowly tailored. Approximately one-third of Google accounts—over 500 million users—have opted into location history, highlighting the ruling's broad impact [1, 3, 4].

Law professor Matthew Tokson said without warrant requirements, the government "could monitor a protest or an abortion clinic or a gun range or a church or an AA meeting or a doctor’s office" using location data [1].

The Supreme Court's decision sets a new legal boundary on how police obtain digital location tracking data and reinforces Fourth Amendment protections for cell phone users nationwide [1, 4].