The key here is “most cases.”
In a 5-4 decision, the court said, “We decline to grant the state unrestricted access to a wireless carrier’s database of physical location information. In light of the deeply revealing nature of CSLI [Cell Site Location Information], its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection. The Government’s acquisition of the cell-site records here was a search under that Amendment.”
Bottom line: Because the acquisition of the CSLI cell records was a search under the Fourth Amendment, police were obligated to get a search warrant before accessing that information.
Therefore, the information was obtained illegally.
Chief Justice John Roberts said the court’s decision is limited to cellphone tracking information. For example, police can still cobntact a phone carrier and collect phone numbers dialed from a particular phone without obtaining a search warrant.
Roberts also noted how the High Court has wrestled with the impact of technology on personal privacy and the extent to which a person can have a reasonable expectation of privacy from government intrusion.