In 1969, the landmark case of Brandenburg v. Ohio established the "imminent lawless action" test for determining when speech is protected by the First Amendment. The Supreme Court ruled that advocating illegal action is protected unless it is intended to incite imminent lawless action, setting a high bar for government restriction of speech.

The Pledge of Allegiance, initially non-compulsory, became mandatory in 1942 after a Supreme Court ruling. However, a later reversal in 1943, based on the First Amendment, prohibited compulsory recitation. This landmark case established that the government cannot compel speech. Today, the Pledge is voluntary, with ongoing debates over its wording and constitutional implications.