https://techcrunch.com/2017/08/15/countless-advocates-and-companies-advise-supreme-court-to-protect-phone-location-data-under-the-4th-amendment/

Among the Supreme Court’s many upcoming cases is Carpenter v. United States, which will settle the question of whether your location and movements, as determined by the ordinary interactions of your phone with the network, are protected by the Fourth Amendment. Dozens of companies, advocates, experts and interested parties just weighed in ahead of the hearing.

The issue, briefly summarized: Timothy Carpenter was convicted partly by the use of 127 days (and 12,898 individual location points) of cell site location information (CSLI) acquired by police from telecoms without a warrant. The argument that this information was protected, and that its collection constituted unreasonable search and seizure, failed to convince the Appeals court.