What is the "overbreadth" doctrine in the context of the First Amendment?

The First Amendment overbreadth doctrine "permits a defendant to make a facial challenge to an overly broad statute restricting speech, even if he himself has engaged in speech that could be regulated under a more narrowly drawn statute." Alexander v. United States, 509 U.S. 544, 555, 113 S.Ct. 2766, 125 L.Ed.2d 441 (1993). This doctrine responds to the concern that "the threat of enforcement of an overbroad law may deter or chill constitutionally protected speechespecially

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