For further information, I would recommend First Amendment Law in a Nutshell, by Jerome A. Barron and C. Thomas Dienes. The book provides a basic discussion of many issues and provides a jumping-off point for further research. Such a designation refers to government agencies and other entities that operate under the direction of government. Under the U.S. Constitution, rights and liberties such as freedom of speech are only protected against interference by state action. The United States Supreme Court, as well as many lower courts, has held that the freedom of expression is not absolute.
Many instances exist where expression has been limited or banned outright.
Fighting words are those that tend to inflict injury or incite a breach of the peace. Unprotected speech may be regulated, criminalized, or banned outright. If speech does not fall within these categories, it is generally protected under the First Amendment. This doesn't mean that the speech cannot be regulated at all, but it does mean that the content of the speech may not be regulated. In other words, if your speech is protected, what you say cannot be limited or censored, but how you say it may be restricted.