At Yale University, you can be prevented from putting an F. Scott Fitzgerald quote on your T-shirt. At Tufts, you can be censured for quoting certain passages from the Quran. Welcome to the most authoritarian institution in America: the modern university-a bizarre, parallel dimension," as Greg Lukianoff, president of the Foundation for Individual Rights in Education [FIRE], calls it. In his new book, Unlearning Liberty: Campus Censorship and the End of American Debate, Mr. Lukianoff notes that baby-boom Americans who remember the student protests of the 1960s tend to assume that U.S. colleges are still some of the freest places on earth. But that idealized university no longer exists. It was wiped out in the 1990s. Today, university bureaucrats suppress debate with anti-harassment policies that function as de facto speech codes. FIRE maintains a database of such policies on its website, and Mr. Lukianoff's book offers an eye-opening sampling. What they share is a view of "harassment" so broad and so removed from its legal definition that, Mr. Lukianoff says, "literally every student on campus is already guilty." Conservatives and libertarians are especially vulnerable to such charges of harassment.