First Amendment
The First Amendment to the U.S. Constitution prevents Congress from passing any law which:
The exact text is at United States Constitution/Amendment One
The consequences of this Amendment to American society have been profound. First Amendment questions have been raised with regard to the separation of church and state; civil rights issues; pornography and obscenity; political speech and organizations; journalism and its restrictions; involuntary commitment laws; and many more.
See: United States Bill of Rights, Jehovah's Witnesses, antidisestablishmentarianism, Lemon test