New York Times Co. v. Sullivan, 376 U.S. 254 (1964), was a landmark U.S. Supreme Court decision that ruled the freedom of speech protections in the First Amendment to the U.S. Constitution restrict the ability of a public official to sue for defamation.

[3] The underlying case began in 1960, when The New York Times published a full-page advertisement by supporters of Martin Luther King Jr. that criticized the police in Montgomery, Alabama, for their treatment of civil rights movement protesters.

[1] The Court reasoned that defending the principle of wide-open debate will inevitably include "vehement, caustic, and...unpleasantly sharp attacks on government and public officials."

On March 29, 1960, The New York Times carried a full-page advertisement titled "Heed Their Rising Voices", paid for by the Committee to Defend Martin Luther King and the Struggle for Freedom in the South.

The constitutional safeguard, we have said, "was fashioned to assure unfettered interchange of ideas for the bringing about of political and social changes desired by the people."

"[15] With this background, the Court framed the case around the question of whether this American constitutional commitment to free speech required loosening traditional defamation laws.

[17] The Court analogized Alabama's libel law to the infamous Alien and Sedition Acts passed in the late 1790s during the presidency of John Adams.

[13] Instead, the Court held that under U.S. law, any public official suing for defamation must prove that the defendant made the defamatory statement with "actual malice".

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.The Court said that besides proving "actual malice", the First Amendment's protections also imposed two other limitations on libel laws.

In England, the development was specifically rejected in Derbyshire County Council v. Times Newspapers Ltd[19] and it was also rejected in Canada in Hill v. Church of Scientology of Toronto[20] and more recently in Grant v. Torstar Corp.[21] In Australia, the outcome of the case was followed in Theophanous v. The Herald & Weekly Times Ltd,[22] but Theophanous was itself overruled by the High Court of Australia in Lange v Australian Broadcasting Corporation (1997) 189 CLR 520.

The editorial board of The New York Times heralded the Sullivan decision not only as a ruling which "instantly changed libel law in the United States", but also as "the clearest and most forceful defense of press freedom in American history.

"[23] The board added: The ruling was revolutionary because the court for the first time rejected virtually any attempt to squelch criticism of public officials—even if false—as antithetical to "the central meaning of the First Amendment."

Its core observations and principles remain unchallenged, even as the Internet has turned everyone into a worldwide publisher—capable of calling public officials instantly to account for their actions and also of ruining reputations with the click of a mouse.

[23]In a 2015 Time magazine survey of over 50 law professors, both Owen Fiss (Yale) and Steven Shiffrin (Cornell) named New York Times v. Sullivan "the best Supreme Court decision since 1960," with Fiss noting that the decision helped cement "the free-speech traditions that have ensured the vibrancy of American democracy" and Schiffrin remarking that the case "overturned the censorial aspects of the law of libel and made it far easier in what’s left of our democracy for citizens—including the Fourth Estate—to criticize the powerful.

[24] Silberman's dissent also accused big tech companies of censoring conservatives and warned that "Democratic Party ideological control" of mainstream media may be a prelude to an "authoritarian or dictatorial regime" that constitutes "a threat to a viable democracy".