A federal appeals court has ruled that geofence warrants, which allow police to collect location data from devices in a specific area, are 'categorically prohibited' by the Fourth Amendment. The court found that such warrants constitute a 'general, exploratory rummaging' that is not allowed under the Constitution. The decision is a significant victory for privacy advocates, who argue that geofence warrants are too broad and can sweep up innocent people's data. The ruling may have implications for law enforcement's use of location data in investigations.