Some state laws ban "criminal harassment," including behavior defined more or less as
Engag[ing] in a course of conduct [= a pattern of conduct composed of a series of acts over a period of time, however short, evidencing a continuity of purpose] or repeatedly commit[ing] acts which harass or intimidate the person and which serve no legitimate purpose.
The broadest body of caselaw I've seen on this has been in Wisconsin; the statute I just quoted is the Wisconsin one, Wisc. Stat. Ann. 947.013. Note that this is a very different provision than "hostile [work/educational/public accommodations/housing] environment harassment," with entirely different elements; all they share is the label "harassment," and the capacity to restrict speech because of its content.
Here's a specific interest that I think helps illustrate the problems with such laws: Several Fond du Lac residents live near a convicted sex offender (a Michael A. Allen). They printed copies of that offender's Wisconsin Department of Corrections Sexual Offender Registry Registrant Information web page, and publicly posted it in various places -- at a gas station, at a YMCA, and several trees and telephone poles. They were then arrested for harassment. The arresting officer's report explains that the arrest happened
because [the arrestees'] conduct served no useful purpose. Michael Allen is following the rules of the registration system and is not breaking any laws. It appears to be the intent of the suspects to force Michael Allen to move from the area.
I take it that defendants believe their conduct does serve a legitimate and useful purpose -- it may inform their neighbors about the possible danger posed by Allen. Even if they intend to try to get Allen to move, that too may be useful for them and their children, though of course it may lead Allen to move to become a possible threat to other children (for reasons I note below, I don't see him as much of a threat, but obviously they do, and the law does require registration for offenders like Allen).
Moreover, the Court has made clear that people have a right to republish public record criminal justice information, even when it consists of the names of rape victims. (See Florida Star v. B.J.F.) Surely people have at least as much right to republish such information about criminals. (For more, see here.) So I think their speech can't be criminalized.
But more broadly, it seems to me that regardless of whether such speech could be prohibited under a clearly and narrowly drafted law, the current law, which punishes "harass[ing]" speech said with "no legitimate purpose" must be unconstitutionally vague. It gives no meaningful guidance to speakers who want to know if they'll be criminally punished, or to police officers, prosecutors, judges, and juries. It thus poses all the problems that Grayned v. City of Rockford (1972) identified as constitutional defects of vague laws:
First, because we assume that man is free to steer between lawful and unlawful conduct, we insist that laws give the person of ordinary intelligence a reasonable opportunity to know what is prohibited, so that he may act accordingly. Vague laws may trap the innocent by not providing fair warning.
Second, if arbitrary and discriminatory enforcement is to be prevented, laws must provide explicit standards for those who apply them. A vague law impermissibly delegates basic policy matters to policemen, judges, and juries for resolution on an ad hoc and subjective basis, with the attendant dangers of arbitrary and discriminatory application.
Third, but related, where a vague statute "abut[s] upon sensitive areas of basic First Amendment freedoms," it "operates to inhibit the exercise of [those] freedoms." Uncertain meanings inevitably lead citizens to "`steer far wider of the unlawful zone' ... than if the boundaries of the forbidden areas were clearly marked."
By the way, Allen's offense (as reported in the press) strikes me as very minor as sex crimes go:
Court records show that Allen was convicted in 1998 of second-degree sexual assault of a child for receiving oral sex from a 15-year-old girl. The records show that Allen was 16 years of age at the time of the incident, which occurred in 1997 in Shawano County. In a victim statement included with court documents, the 15-year-old girl said it was her idea to perform the sexual act. She also wrote that she didn't think it was Allen's fault or that he should get in trouble.
It seems to me that even if consensual 16-/15-year-old sex should be criminalized, it should not be subject to sex offender reporting (certainly not longterm reporting), or at least any such reports should clearly note the nature of the offense (something the Wisconsin sex offender page does not). Such reporting is not only unfair to the offender, but also harmful to the community, because it misleads the public into overestimating this threat, and distracts them from other possible threats.
Nonetheless, while this would have been good reason for Wisconsin not to place Allen's records on the sex offender site (unless there was something more to the sexual contact than the newspaper reports), and this might make the neighbors' actions morally suspect (if they knew the nature of Allen's crimes), it doesn't strip the actions of constitutional protection. The First Amendment includes the right to convey information even about crimes that many may consider minor (though note that Wisconsin law, which makes the crime a felony and a reportable sexual offense). One might argue that the neighbors' speech is so incomplete as to be false, but I don't think that's right; I take it, for instance, that newspapers couldn't be criminally prosecuted if they accurately reported that someone was convicted of a certain crime, but failed to give all the details that might show how minor the crime was, and the same must be true here. And in any event, none of the facts of Allen's case can remotely justify punishing speakers under the amorphous "no legitimate purpose" standard.
Note also that the same defendants were also arrested for getting into a fight with the offender over the offender's coming onto their property to remove a copy of the sheet that they had posted on their own property. That, though, is a separate charge, which I'm setting aside for now.