On June 22, the Supreme Court released its long-awaited ruling in Carpenter v. United States, a case challenging whether law enforcement agencies need a search warrant to acquire the history of a cell phone's location from a wireless provider. Chief Justice John Roberts wrote for the five-justice majority that doing so amounts to a 4th Amendment search, a decision that will have far-reaching implications for law enforcement activities moving forward. On Thursday, Benjamin Wittes spoke on the phone with Jim Baker, the former general counsel of the FBI, and Orin Kerr, the 4th Amendment expert whose writing was cited in every dissent, to understand the decision. They talked about what the decision said, what a warrant for cell site data might look like, and the ruling's implications for other areas of 4th Amendment law.