Free speech is indispensable on college campuses, essential to learning and the pursuit of truth. But free speech does not mean a free-for-all. A university that values free expression still has to regulate some speech to enable its educational mission. So how can we distinguish reasonable restrictions from impermissible infringement? In this clear-headed, no-nonsense explainer, Cass Sunstein takes us briskly through a wide range of scenarios involving students, professors, and administrations. he shows, for instance, why it's consistent with the First Amendment to punish students who shout down a speaker, but not those who chant offensive slogans; why a professor cannot be fired for writing controversial op-eds, yet an applicant's political views can be considered in hiring decisions. And he explains why private universities, through not legally bound by the First Amendment, would be well advised in most cases to follow it nonetheless.