Libel, slander, and private action
American tort liability for defamatory speech or publications—slander and libel—traces its origins to English law. The nature of American defamation law was vitally changed by the Supreme Court in 1964, in deciding New York Times Co. v. Sullivan 376 U.S. 254 (1964). The New York Times had published an advertisement indicating that officials in Montgomery, Alabama had acted violently in suppressing the protests of African-Americans during the Civil rights movement. The Montgomery Police Commissioner, L. B. Sullivan, sued the Times for libel on the grounds that the advertisement damaged his reputation. The Supreme Court unanimously overruled the $500,000 judgment against the Times. Justice William J. Brennan suggested that public officials may sue for libel only if the publisher published the statements in question with "actual malice."
The actual malice standard applies to both public officials and public figures, including celebrities. Though the details vary from state to state, private individuals normally need only to prove negligence on the part of the defendant.
In Greenbelt Cooperative Publishing Association, Inc. v. Bresler, 398 U.S. 6 (1970), the Supreme Court ruled that a Greenbelt News Review article, which quoted a visitor to a city council meeting who characterized Bresler's aggressive stance in negotiating with the city as "blackmail", was not libelous since nobody could believe anyone was claiming that Bresler had committed the crime of blackmail and that the statement was essentially hyperbole (i.e., obviously an opinion).
The Supreme Court ruled in Gertz v. Robert Welch, Inc. 418 U.S. 323 (1974), opinions could not be considered defamatory. It is thus permissible to suggest, for instance, that someone is a bad lawyer, but not permissible to falsely declare that the lawyer is ignorant of the law: the former constitutes a statement of values, but the latter is a statement alleging a fact.
More recently, in Milkovich v. Lorain Journal Co., 497 U.S. 1 (1990), the Supreme Court backed off from the protection from "opinion" announced in Gertz. The court in Milkovich specifically held that there is no wholesale exemption to defamation law for statements labeled "opinion," but instead that a statement must be provably false (falsifiable) before it can be the subject of a libel suit.
Hustler Magazine v. Falwell, 485 U.S. 46 (1988) extended the "actual malice" standard to intentional infliction of emotional distress in a ruling which protected a parodic caricature. In the ruling, "actual malice" was described as "knowledge that the statement was false or with reckless disregard whether or not it was true."
Ordinarily, the First Amendment only applies to prohibit direct government censorship. The protection from libel suits recognizes that the power of the state is needed to enforce a libel judgment between private persons. The Supreme Court's scrutiny of defamation suits is thus sometimes considered part of a broader trend in U.S. jurisprudence away from the strict state action requirement, and into the application of First Amendment principles when private actors invoke state power.