Hillary: The Movie, a documentary produced by the nonprofit group Citizens United, which did not wish to see Senator Clinton elected president. Because McCain-Feingold prohibits so much as mentioning a candidate’s name in pre-election communications paid for by certain disfavored groups — unions and “corporations” — the filmmakers were informed by a federal judge that showing their work would constitute a crime. The filmmakers sued, and the case is Citizens United v. Federal Election Commission. Mr. Stewart is defending the government’s ban on this film; the same rules that apply to a campaign commercial apply to a documentary film, his reasoning goes. Justice Alito alertly pressed Mr. Stewart on that issue: If commercials and films are covered, how about books? How about campaign biographies? Yes, Mr. Stewart answered, the U.S. government is prepared to ban books, under certain circumstances, and is legally empowered by McCain-Feingold to do so. Jaws dropped, black robes fluttered.