According to the U.S. Supreme Court, historical cellphone records deserve more stringent protection than other customer information held by service providers. In Carpenter v. United States, the Court recently ruled that the collection of historical cell-site location information during a criminal investigation is subject to Fourth Amendment “search and seizure” protection and that the federal government generally needs a warrant to access such records. The decision may have been a victory for privacy advocates in theory, but what does it mean on the ground for government investigations and the companies that handle this and related data? This article analyzes the decision and its implications with insight from our experts. See also “How to Respond to Law Enforcement Demands for Geolocation Data and Data Stored Abroad” (Nov. 30, 2016).