The Court continued: In mechanically applying the third-party doctrine to this case the Government fails to appreciate the lack of comparable limitations on the revealing nature of CSLI. Nor does the second rationale for the third-party doctrine— voluntary exposure—hold up when it comes to CSLI. Cell phone location information is not truly “shared” as the term is normally understood. First, cell phones and the services they provide are “such a pervasive and insistent part of daily life” that carrying one is indispensable to participation in modern society. Riley, 573 U. S., at ___. Second, a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the user’s part beyond powering up.
This decision is narrow. It does not express a view on matters not before the Court; does not disturb the application of Smith and Miller or call into question conventional surveillance techniques and tools, such as security cameras; does not address other business records that might incidentally reveal location information; and does not consider other collection techniques involving foreign affairs or national security. The Government did not obtain a warrant supported by probable cause before acquiring Carpenter’s cell-site records. It acquired those records pursuant to a court order under the Stored Communications Act, which required the Government to show “reasonable grounds” for believing that the records were “relevant and material to an ongoing investigation.” 18 U. S. C. §2703(d). That showing falls well short of the probable cause required for a warrant. Consequently, an order issued under §2703(d) is not a permissible mechanism for accessing historical cell-site records. Not all orders compelling the production of documents will require a showing of probable cause. A warrant is required only in the rare case where the suspect has a legitimate privacy interest in records held by a third party. And even though the Government will generally need a warrant to access CSLI, case-specific exceptions—e.g., exigent circumstances—may support a warrantless search.
Justice Roberts’ holding that “the decision is narrow” is a response to the Government’s argument in favor of allowing warrantless cell-site data dumps. It is a common tactic for the Government to justify its violations of civil liberties by claiming that doing so is necessary to for “national security.”