Check out this 2009 D.C. law that purports to ban “stalking” (D.C. Code §§ 22-3132, -3133), and that provides, among other things:
“Emotional distress” means significant mental suffering or distress that may, but does not necessarily, require medical or other professional treatment or counseling….
“To engage in a course of conduct” means directly or indirectly, or through one or more third persons, in person or by any means, on 2 or more occasions, to:
(A) Follow, monitor, place under surveillance, threaten, or communicate to or about another individual;
(B) Interfere with, damage, take, or unlawfully enter an individual’s real or personal property or threaten or attempt to do so; or
(C) Use another individual’s personal identifying information [defined to include a person’s name]….
(a) It is [a crime] for a person to purposefully engage in a course of conduct directed at a specific individual [to intentionally, knowingly, or negligently] cause that individual to … [s]uffer emotional distress….
(b) This section does not apply to constitutionally protected activity.
So if you twice say something about someone, where a reasonable person should have known that this would cause the subject “significant mental suffering or distress,” you’re guilty of a misdemeanor — or a felony if the subject is under 18, and you are four or more years older than the subject — unless the court finds your speech to be “constitutionally protected activity.”
But what is constitutionally protected activity? For instance, is telling some friends about an acquaintance’s medical history or sex life constitutionally protected? The Court has had no occasion to decide this, partly because such private revelation is usually not even tortious under state law (in most states, the “disclosure of private facts” tort only covers speech to the public at large, or under circumstances where it’s likely to reach the public) and thus the matter rarely comes to court. How about marketing T-shirts or video games or comic books that contain a celebrity’s name or likeness? Lower courts are split on that. What about saying something that violates a promise not to say it? That’s constitutionally unprotected against a breach of contract lawsuit, but the Court has never decided it whether it can generally be criminalized.
Or how about residential picketing? Such speech is unprotected against a sufficiently narrow content-neutral residential picketing ban, but protected against content-based bans, and protected against even content-neutral bans that are too broad (e.g., apply to all picketing within 300 feet of a residence, rather than just picketing right in front of a residence). More broadly, the same speech is often protected against some sorts of restrictions but unprotected against others that are sufficiently narrowly tailored to some government interest.
To be sure, some courts have upheld laws that have such supposed “savings clauses,” but others have struck them down. And it seems that the latter view is the correct one; in the words of Long v. State (Tex. Ct. Crim. App. 1996) (paragraph break added):
While the provision would permit the defendant to introduce evidence before the jury regarding the constitutional nature of his conduct, it would relegate the First Amendment issue to a “case-by-case adjudication,” creating another vagueness problem. In essence, (a)(7)(A) [the Texas provision involved in Long -EV], as modified by the affirmative defense, would read something like “it is a crime to intentionally annoy someone unless by that conduct the actor engages in activity protected by the First Amendment.” Application of the affirmative defense to subsection (a)(7)(A) on a case-by-case basis would require people of ordinary intelligence — and law enforcement officials — to be First Amendment scholars. Arguably, people are always “on notice” that constitutionally protected conduct is exempt from prosecution, and law enforcement officials could always look to the First Amendment to determine when a law should not be enforced because it would interfere with constitutionally protected activity. But, the mere existence of the First Amendment has never been held automatically to cure vagueness problems implicating First Amendment freedoms.
Because First Amendment doctrines are often intricate and/or amorphous, people should not be charged with notice of First Amendment jurisprudence, and a First Amendment defense cannot by itself provide adequate guidelines for law enforcement. [Footnote: Charging ordinary citizens and law enforcement officials with knowledge of constitutional law seems especially inappropriate in an area of law, such as stalking, that is relatively new.] Moreover, an attempt to charge people with notice of First Amendment caselaw would undoubtedly serve to chill free expression.
UPDATE: I should note that I think the Texas court’s argument is correct whether or not the “constitutionally protected activity” proviso creates an affirmative defense as to which the defendant must introduce evidence, or creates an element of the crime (the lack of constitutional protection for the activity) that the prosecution must prove. Even if the prosecution must prove that the activity is constitutionally unprotected, the provision remains so unclear that it’s unconstitutional, either under the void-for-vagueness doctrine as such or (as in Reno v. ACLU) because the vagueness of the law leads it to deter even constitutionally protected speech.