The First Amendment declares that 'Congress shall make no law . . . abridging the freedom of speech , or of the press. . . . ' Yet, in the following 200 years, the Supreme Court has defined certain categories of expression-the obscene, the defamatory, commercial, and fighting words or disruptive expression-as constitutionally unprotected. Noted legal scholar David O'Brien provides a history of each category of unprotected speech and puts into bold relief the larger questions of what kinds of expression should (and should not) receive First Amendment protection.