The correct response is: New York Times v. Sullivan determined that actual malice must be proven to pursue charges of libel in the case of a public official.
This landmark decision established that public officials must prove "actual malice"—meaning that the statement was made with knowledge of its falsity or with reckless disregard for the truth—to win a libel suit. This standard significantly expanded freedom of speech by making it more difficult for public officials to silence critics through libel lawsuits.