| Term | Definition |
| Schenk v. US (1919) | Man mailed leaflets against the draft during World War 1. This set up the 'clear and present danger' rule because it threatened national security. |
| Brandenburg v. Ohio (1969) | A KKK rally had a lot of televised racist speech, but it was found that inflammatory speech cannot be restricted unless it creates "imminent lawless action" |
| Yates v. US (1957) | Leaders of the Communist Party were convicted under the Smith Act which barred teaching and advocating the overthrow of the government. Here the courts drew a line between speech and actual action, saying it was okay to say something as long as you didn't act upon it. |