Anyone wondering about freedom of speech in the U.S. would do well to read this portable document file:
Freedom of Speech and Press Exceptions to the First Amendment. It's from the Congressional Research Service and was provided to the public by the
Federation of American Scientists via its
Secrecy News electronic-mail newsletter.
The sections on obscenity and pornography might be useful, since people involved in anime/games/manga seem to frequently speculate on those topics. Similar documents pertaining to other nations' laws would be quite helpful as well, I should think.
=^..^=