Although the language of the First Amendment refers to freedom of speech, it turns out that most of the vast universe of speech remains untouched (and thus unprotected) by the First Amendment. Antitrust law, the law of securities regulation, the law of criminal solicitation and conspiracy, much of labor law, most of the law of evidence, most of the law of sexual harassment, along with scores of other examples, involve legal control of speech that is well understood to lie beyond the boundaries of the First Amendment’s concerns. It is not that some of these regulations satisfy a higher burden of justification imposed by the First Amendment. Rather, it is that the First Amendment does not even show up in the analysis. But if we look for an explanation of why the speech that lies beyond the boundaries of the First Amendment remains outside the First Amendment’s ken, we find that explanation not in the theory of freedom of speech or the legal doctrine of the First Amendment, but instead in an often serendipitous array of political, cultural, social, and economic factors that determine what makes the First Amendment salient in some instances of speech regulation but not in others. If we examine First Amendment salience more closely, we see that the First Amendment’s special political and cultural place in American society gives it a kind of magnetism that leads a wide variety of legal and political claims to migrate to the First Amendment. But we see as well that numerous other non-legal factors determine, far more than legal factors, which of those opportunistic claims to First Amendment attention will succeed and which will not.
Schauer, Frederick. "The Boundaries of the First Amendment: A Preliminary Exploration of Constitutional Salience." KSG Faculty Research Working Papers Series RWP03-024, April 2003.