As the technology for regulating travel has evolved from passports and rubber stamps to include retina scans and digital databases, the bureaucratic structure of the American system for regulating international travel has grown from a small office in Washington, DC, to a highly sophisticated network spanning the globe. The U.S. government now controls a web of surveillance---from extra frisks at airport security to complete bans on travel by sea or air---with the potential to snare almost anyone. These programs are top secret, and the names on the No Fly List are classified. There is no notice and no appeal. In tracing the history and scope of U.S. travel regulations, Jeffrey Kahn begins with the fascinating story of Mrs. Shipley, a federal employee who almost single-handedly controlled access to passports during the Cold War. He questions how far national security policies should go and whether the government should be able to declare some individuals simply too dangerous to travel. An expert on constitutional law, Kahn argues that U.S. citizens' freedom to leave the country and return is a fundamental right, protected by the Constitution.