Libel law changed forever in 1964 with the United States Supreme Court decision in New York Times v. Sullivan. That decision and others by the Warren Court established a clear concept of libel and one that guaranteed press freedom without eliminating libel entirely.
The Supreme Court held in the Times case that the Constitution, specifically the First Amendment, prohibits a public official from recovering damages for a defamatory falsehood related to his or her official conduct. The court included one qualification: malice, or actual malice. The definition given for actual malice was “with knowledge that it (the material in question) was false or with reckless disregard of whether if was false or not.”.:

The Supreme Court had no other choice in that case. Deciding otherwise would have shackled the press at the very time public debate was needed on important social issues. In the Times case the issue was segregation. Later it was to be the Vietnam War in the Pentagon Papers case, then President Richard Nixon’s right to withhold tapes and so on. Any other decision by the Supreme Court in the Times case would have changed history—and not for the better.

After establishing this new standard for public officials, the Supreme Court used other decisions to limit suits brought by public figures and private citizens.
Two cases were decided in one opinion in 1967. They were Associated Press v. Walker and Curtis Publishing Company v. Butts. In that decision the Supreme Court brought public figures under the umbrella it had created in Sullivan.
The court said that a public figure cannot collect damages unless malice is proved. The court established a guideline, “accepted publishing standards,” by which reckless disregard might be judged.
In 1971 in Rosenbloom v. Metromedia, Inc. the Supreme Court held that a private citizen involved in an event of public interest must prove malice to collect in a libel action.