Chilling Effect

Justice Felix Frankfurter introduced the underlying concept in his 1952 concurring opinion in Wieman v. Updegraff, warning that loyalty oaths had "an unmistakable tendency to chill" academic freedom. Justice William Brennan named and codified the doctrine in Lamont v. Postmaster General (1965), striking down a postal regulation requiring recipients of "communist propaganda" to register with the government. Both cases arose in the McCarthy era; the chilling effect doctrine has since become a cornerstone of First Amendment jurisprudence.