The right to free speech appears to be spelled out clearly in the Constitution, but it doesn't protect all forms of speech. Throughout the early to mid-20th century, the Supreme Court spelled out various limits to the meaning of free speech – specifically seditious speech. Seditious speech is a form of speech that advocates overthrowing the United States. The era of the Supreme Court's seditious speech jurisprudence began with the World War I era case, Schenck v. U.S.
Charles Schenck was arrested for violating Section 3 of the Espionage Act of 1917, which prohibited interference with the military operations of the United States. Schenck sent out 15,000 leaflets to impending military draftees, urging them to not go through with the draft as it constituted "involuntary servitude." Schenck argued that the First Amendment allowed him to distribute the leaflets and that his arrest under the Espionage Act was unconstitutional.
The Supreme Court disagreed under an often cited opinion by Oliver Wendell Holmes Jr. Holmes, who understood that the First Amendment has limits which are best exemplified by the famous quote: "The most stringent protection of free speech would not protect a man in falsely shouting fire in a theater and causing a panic."
Holmes created the "clear and present danger" test which allowed the Supreme Court to restrict free speech. In the case of Schenck, the leaflets were meant to impede the draft during the nation's war effort and constituted as "clear and present danger."
Abrams v. U.S. was a follow-up case to Schenck's. In this case, Jacob Abrams, along with several others, was arrested under the 1918 Sedition Act after distributing flyers that urged munition workers to impede the U.S. war effort against Germany. The Supreme Court upheld the arrests under the Sedition Act and created a new standard known as the bad tendency test for reviewing seditious speech. The court held that if the seditious speech had the possibility of or already had a bad tendency to bring upon criminal wrongs, the speech could be restricted. The justice system shifted away from the higher threshold of "clear and present danger" used to restrict speech in Schenck's case to just assessing whether the speech had "bad tendency."
The standard to address seditious speech wasn't fully challenged until the 1969 case of Brandenburg v. Ohio. Clarence Brandenburg was a local leader of the KKK and gave a speech which advocated for violence against minorities and Jews. Brandenburg's speech violated Ohio's syndicalism law, and he was promptly arrested. The Supreme Court overturned Brandenburg's arrest and created a much greater threshold to restrict seditious speech by enacting the imminent lawless action test.The seditious speech could be curtailed only if it intended for an imminent criminal action to occur rather than just expressing "bad tendency."
Thus, today the Supreme Court has radically shifted from the limit established in Abrams v. U.S.
