by Charles Kim*
The Supreme Court’s decision in Chatrie v. United States fundamentally altered the constitutional landscape governing so-called “geofence warrants” by holding that when the government acquires comprehensive location history data, it must first obtain a warrant which satisfies the Fourth Amendment’s probable cause and particularity requirements. But Chatrie left a critical question unanswered: how would a constitutionally valid geofence warrant meet those requirements? This Contribution argues that the warrant at issue in Chatrie fell short because it authorized an increasingly intrusive search while leaving nearly every consequential decision to law enforcement officers rather than a neutral magistrate. Although anonymization of location data can substantially mitigate the privacy concerns associated with its disclosure, it is meaningful only if accompanied by safeguards that prevent premature de-anonymization. Building on these principles, this Contribution proposes a model geofence warrant that would require renewed judicial authorization before each expansion of the search. By restoring judicial oversight, the model warrant better reconciles legitimate law enforcement needs with the Fourth Amendment’s historical commitment to protecting privacy from unbounded government discretion.