A Missouri public schoolteacher is seeking to stop a state law limiting teachers’ contact with students on social networks, calling it unconstitutional and a violation of protected free speech rights.

The prohibitions against online use are part of a broader law seeking to protect children from sexual predators in the classroom.

The law, formally titled the “Amy Hestir Student Protection Act,” was signed by Gov. Jay Nixon July 14 and goes into effect Aug. 28. It forces school districts to draft a policy by Jan. 1, 2012 that, among other protections, prohibits teachers from entering private communication with students and former school-age students via Facebook and other social networks.

In her class action complaint filed in federal court, teacher Christina Thomas is seeking a temporary injunction against the law, saying it violates her free speech rights protected by the first and 14th amendments.

Although the law was intended to guard students against sexual predators, Ms. Thomas says it “is unconstitutionally vague in that it fails to provide people of ordinary intelligence a reasonable opportunity to understand what conduct it prohibits, authorizes, or encourages.” She says the law is unnecessarily broad and even puts teachers in jeopardy when using social networks to communicate with their own school-age children.

The Missouri Teachers Association is also challenging the law on similar grounds. The organization’s separate complaint, filed in state court Friday, calls the law “so vague and overbroad” that lawmakers “cannot know with confidence what conduct is permitted and what is prohibited and thereby ‘chills’ the exercise of first amendment rights of speech, association, religion, collective bargaining and other constitutional rights by school teachers.”

Sen. Jane Cunningham (R), who sponsored the bill, defends the law, saying it “in no way stops communication with students.” The law says teachers can only communicate online with students if the website “is available to school administrators and the child’s legal custodian.”

Anthony Rothert, legal director of the American Civil Liberties Union of Eastern Missouri, which is representing Thomas, says his client was alarmed after she learned her school district would impose disciplinary action against teachers if it discovered teachers were using Facebook even when communicating with their own children or others of school-age involved in outside school activities such as Sunday school class, athletic teams, or Scout troops. Mr. Rothert says Thomas has three school-age children of her own.

“She’s facing the choice of either defying what she was told by her employer or refraining from doing it even though she might not be caught,” Rothert says. Either way, “both of those constitute enough of an injury under the first amendment to get relief.”

Facebook and other social networks have emerged in recent years as tools teachers often tap to communicate with students outside campus. The sites are often used as a way to share notes, review papers, answer questions or, on the rare occasion, offer emotional support.

Rothert says the law will “affect the most vulnerable” in the classroom because it will remove access to a “trusted adult that kids turn to when they’re in need and can’t talk to their parents.”

However, the argument that the law is unconstitutional because it prevents teachers from communicating with their own children may not be enough to “justify striking down the statute on its face,” says Alan Brownstein, a constitutional law expert who teaches at the University of California School of Law, Davis.

Because the law is so difficult to enforce, Mr. Brownstein says it would be hard for prosecutors to show injury; in fact, teachers, if caught, may find it easy to demonstrate in a courtroom that they were communicating with their own children.

Mr. Brownstein says the case is important for showing just how murky free speech principles have become due to the advent of social media, which is rapidly breaking down the traditional lines between public and personal spheres, which until recently, were relatively easy to regulate.

“All the conventional boundaries no longer apply because location used to matter,” he says. “But what happens when you’re in a world where location doesn’t matter, where speech is not grounded in any place and being in a particular location doesn’t mean you can’t be in communication to or receive communication from anybody else in the world?”

Like cyber bullying, social network use among teachers and students is forcing courts on both the state and federal level to rethink free speech rights on campus. But the waters remain murky under Missouri's new law. Teachers could be protected if they use social networks as an outreach of their classroom activities, but the line would be crossed if they started proselytizing for their religious or political beliefs, for example.

In that case, they could face the same disciplinary action that they might if they did the same in the classroom. This scenario would require context, which the current law does not provide, says Chad Flanders, an assistant law professor at St. Louis University’s law school.

Mr. Flanders, who considers the law as “clumsily-written,” says it’s “one-size-fits-all” approach to social networks is not effective because it does not take into account how the technology is now the primary mode of communication among young people, particularly in how they share information with their peers, including adults.

He says instead of a state mandate, the decision on how to regulate social network use in and outside the classroom should be left to local school districts, as is the case for most states.

“The hope is that the more local you make it, the more discussions you have, the more feedback from teachers there is, which can result in a more nuanced law,” he says.

The Missouri law, as written, may not even be effective in preventing sexual predators from using social networks to contact children, Flanders says, because it will likely “drive [predators] back to the phone or private contact." Online interaction, on the other hand, leaves an e-paper trail, which will make it easier for law enforcement to track.