From 1791 to the present... the First Amendment has permitted restrictions upon the content of speech in a few limited areas, and has never included a freedom to disregard these traditional limitations. These historic and traditional categories long familiar to the bar-including obscenity, defamation, fraud, incitement, and speech integral to criminal conduct-are well-defined and narrowly limited classes of speech, the prevention and punishment of which have never been thought to raise any Constitutional problem.
U.S. v. Stevens.
Although the First Amendment stands against any freewheeling authority to declare new categories of speech outside the scope of the First Amendment, the Court has acknowledged that perhaps there exist some categories of speech that have been historically unprotected but have not yet been specifically identified or discussed in our case law. Before exempting a category of speech from the normal prohibition on content-based restrictions, however, the Court must be presented with persuasive evidence that a novel restriction on content is part of a long (if heretofore unrecognized) tradition of proscription.
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