The Free Speech Clause protects false speech without violating the First Amendment, but make sure you understand and recognize there are other types of free speech not permitted, and can get you into serious trouble with the FTC and the U.S. Constitution.
Ms. Cauldwell presents two landmark cases: one by Chief Justice Vinson in Dennis v. United States in 1951, and another by early 20th-century Justice Oliver Wendell Holmes, who developed a framework that continues to influence First Amendment law today.