In the summer of 1964, Clarence Brandenburg, a leader in the Ku Klux Klan, gave a speech at a Klan rally. Because of this speech — which included remarks accusing the United States government of suppressing the “Caucasian race” — he was convicted of advocating violence under the Ohio Criminal Syndicalism Statute. The syndicalism law made it illegal to advocate "crime, sabotage, violence, or unlawful methods of terrorism as a means of accomplishing industrial or political reform."
After his initial conviction, Brandenburg agreed to be represented by the ACLU of Ohio. Volunteer attorney Allen Brown took the case and the national ACLU agreed to fund the eventual U.S. Supreme Court challenge.
On June 9, 1969, the Supreme Court held that the Ohio law violated Brandenburg's right to free speech. The court found that the Ohio Criminal Syndicalism Statute ignored whether or not the advocacy it criminalized actually led to imminent lawless action. The failure to make this distinction rendered the law overly broad and in violation of the Constitution.
Read the U.S. Supreme Court decision.