Kathleen Ann Ruane, Freedom of Speech and Press: Exceptions to the First Amendment (CRS Report 95-815) (Oct. 16, 2009) (full-text).
The First Amendment to the United States Constitution provides that “Congress shall make no law ... abridging the freedom of speech, or of the press.” This language restricts government's ability to constrain the speech of citizens.
The prohibition on abridgment of the freedom of speech is not absolute. Certain types of speech may be prohibited outright. Some types of speech may be more easily constrained than others. Furthermore, speech may be more easily regulated depending upon the location at which it takes place.
This report provides an overview of the major exceptions to the First Amendment — of the ways that the U.S. Supreme Court has interpreted the guarantee of freedom of speech and press to provide no protection or only limited protection for some types of speech. For example, the Court has decided that the First Amendment provides no protection for obscenity, child pornography, or speech that constitutes what has become widely known as "fighting words." The Court has also decided that the First Amendment provides less than full protection to commercial speech, defamation (libel and slander), speech that may be harmful to children, speech broadcast on radio and television (as opposed to speech transmitted via cable or the Internet), and public employees' speech.
Even speech that enjoys the most extensive First Amendment protection may be subject to "regulations of the time, place, and manner of expression which are content-neutral, are narrowly tailored to serve a significant government interest, and leave open ample alternative channels of communication." Furthermore, even speech that enjoys the most extensive First Amendment protection may be restricted on the basis of its content if the restriction passes "strict scrutiny" (i.e., if the government shows that the restriction serves "to promote a compelling interest" and is "the least restrictive means to further the articulated interest").
This report outlines many of the standards the government must meet when attempting to regulate speech in a constitutional manner.