Justice William Brennan (majority): “A rule compelling the critic of official conduct to guarantee the truth of all his factual assertions—and to do so on pain of libel judgments virtually unlimited in amount—leads to a comparable self-censorship….

“The constitutional guarantees require, we think, a federal rule that prohibits a public official from recovering damages for a defamatory falsehood relating to his official conduct unless he proves that the statement was made with actual malice—that is, with knowledge that it was false or with reckless disregard of whether it was false or not.”