Another case similar to Schenck v. United States is Brandenburg v. Ohio, decided in 1969. This case involved a leader of the Ku Klux Klan who was convicted under an Ohio law for advocating violence and illegal activities. The Supreme Court ruled that the state could not punish speech that urged illegal action unless that speech was likely to produce imminent lawless action.
The significance of Brandenburg v. Ohio lies in its refinement of the standards for protected speech under the First Amendment. While Schenck established that speech could be limited during wartime or when it presented a clear and present danger, Brandenburg shifted the standard to focus on whether the speech directly incited imminent lawless action. This case is crucial in understanding the evolution of free speech protections in the United States.