The Courts have ruled over time that most, but not all, speech is protected by the Court system. The unprotected forms of speech are generally
- sedition (presenting a clear threat to overthrow the government),
- obscenity (mostly just hard-core or child porn)
- "fighting words," (those which incite a hostile reaction)
- defamation (slander or libel against a public figure),
- some commercial speech (what businesses advertise, etc)
(taken from RioSalado Online, POS222 American Constitution)