The Doctrines of Substantial Overbreadth and Vagueness
The issue: When may someone whose speech or conduct is not constitutionally protected argue successfully that the statute under which he or she is punished must nonetheless be struck down because it reaches too much protected speech?  When is a law unconstitutionally vague?
Introduction
First Amendment challenges can be grouped into two general categories: as applied challenges and facial challenges.   An as applied challenge says, in effect, "my speech is protected by the First Amendment."  A facial challenge, on the other hand, says "my speech might or might not be protected by the First Amendment, but nonetheless the law under which I'm begin punished reaches too much speech that clearly is protected and therefore must be struck down." 

The Supreme Court has developed the doctrine of substantial overbreadth to deal with facial challenges.  The doctrine recognizes that almost any law regulating speech, even when the vast majority of prohibited speech is not protected by the First Amendment, will seem to potentially reach some speech that is protected by the First Amendment.  The precise reach of a statute is sometimes difficult to determine and persons who draft statutes can't be expected to anticipate every possible application of a law that must necessary be written in somewhat general terms.  To strike down every  law that  had even one potentially impermissible application to protected speech would leave legislators powerless to deal with what might be serious threats to the public welfare or safety.  In recognition of the difficulty legislators face, the Supreme Court announced in Broadrick v Oklahoma (1973) that to invalidate a law on its face it must find "the overbreadth of the statute must not only be real but substantial as well, judged in relation to the statute's plainly legitimate sweep."  (Of course, a person engaging in protected speech under a statute that is overbroad, but not substantially overbroad, could succeed in an as applied challenge to the law.)

Although the substantial overbreadth test announced in Broadrick made it more difficult to facially challenge,  the  Court  has  found a number of laws to fail even its more relaxed standard.  For example, in Board of Airport Commissioners v Jews for Jesus (1987) the Court found facially invalid a regulation adopted by the Board of Airport Commissioners for Los Angeles Airport that stated the airport was "not open for First Amendment activities by any individual."  The Court chose not to decide whether the specific activity in which the challenger engaged  (distributing religious literature in a  terminal walkway) might have been banned under a more narrowly  drafted  regulation.
In Virginia  v Hicks (2003)  the Court rejected an overbreadth challenge to a municipal housing authority  trespass  law.   The law  allowed arrest  of  any  nonresident of a housing project who could not  demonstrate "a legitimate business or social policy for being on the premises."  The Court, in an opinion by Justice Scalia, indicated that if would rarely, if ever, uphold an overbreadth challenge against regulations that were not primarily directed to speech or speech-related conduct. 
 
Cases
Broadrick v Oklahoma (1973)
Bd. of Airport Commissioners v Jews for Jesus (1987)
Virginia v Hicks (2003)


Terminal at LAX where Jews for Jesus sought to hand out literature
 
The Doctrine of Vagueness
Related to the overbreadth doctrine is the doctrine of vagueness.  The vagueness doctrine, an aspect of the due process requirement of notice, holds that a law is facially invalid if persons of "common intelligence must necessarily guess as at its meaning and differ as to its application."  The Court has indicated that a higher decree of clarity is demanded when the law in question threatens fundamental First Amendment Rights.
As an overbreadth concern might be cured by a narrowing interpretation by a state court, so too a vagueness problem that appears on the face of the statute might be cured by means of a clarifying judicial interpretation (a "saving construction") by a state court.

Questions
1. If it is clear that the challenger's speech or conduct could constitutionally be prohibited, why strike down a law that might reach someone else's constitutionally protected speech?
2.  Won't the line between "substantial overbreadth" (unconstitutional) and just plain overbreadth (constitutional) be a fuzzy one?  Should the Court require a particular ration of unconstitutional applications of a law to constitutional applications in order for an overbreadth challenge to be successful?  Can you suggest any principles that would help clarify when a law should be struck down on facial grounds?
3.  Should the Court adopt a bright-line rule that rejects all overbreadth challenges when the law in question is not primarily aimed at expressive activity?
4.  Does the doctrine of substantial overbreadth remove the incentive that legislators might otherwise have had under a more exacting standard of judicial review to draft more precise statutes, with only a very few potentially unconstitutional applications?
5.  Which of the laws challenged on vagueness grounds, the Cincinnati ordinance involved in Coates or the New York regulation of teachers involved in Keyishian, presents the stronger case for a challenge?  Why?
6.  If the Court were to rigorously apply the demanding standard of clarity it used in Keyishian, what other types of regulations might be vulnerable to challenge?
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