Editor’s note: This is the first in a two-part series.

In Carpenter v. United States, No. 16-402 (S.Ct. June 22, 2018), the U.S. Supreme Court held that the Fourth Amendment prohibited the government from using the Stored Communications Act, 18 U. S. C. Section 2703(d) (the SCA), to obtain from wireless cellphone carriers the “time-stamped record known as cell-site location information (CSLI),” which records (as explained below), created over time and saved, can, when looked at together, provide a picture of the public movements of the cellphone user. The court so held because it determined that the government needed to show probable cause to obtain a court order compelling the carrier to surrender its CSLI records to the government, while the SCA required only that the government show “specific and articulable facts” (generically referred to as reasonable suspicion) to obtain from internet service providers (ISPs) records 180 days old or older, i.e., a lower showing of proof than “probable cause” and so one insufficient to obtain the records consistently with the Fourth Amendment.