In 1986, Congress passed the Electronic Communications Privacy Act, a broad framework detailing how law enforcement could conduct surveillance on burgeoning digital communications networks. But the dawn of the Internet as a mass medium, the increasing ubiquity of location-sensitive mobile devices, and the explosive growth of cloud computing have radically changed the technological landscape since then. Yet the law remains largely stuck in the 80s, a 20th century legal operating system for 21st century communications — leaving courts unclear on questions as basic how much privacy protection e‑mail enjoys. Cato Institute research fellow Julian Sanchez discusses how best to update ECPA for this century and beyond.