Three US judges have refused to declare unconstitutional a law that makes it a crime to send obscene material over the internet to minors, because those bringing the case had not put forward enough evidence to show a substantial chilling of free speech.

The case was brought by the National Coalition for Sexual Freedom (NCSF), a group committed to protecting freedom of expression among consenting adults, and Barbara Nitke, a fine art photographer who explores sexual relationships in her work.

The case concerns the controversial Communications Decency Act of 1996 (CDA), the effect of which was greatly reduced in 1997, when the Supreme Court stuck down a provision that criminalised any “indecent” or “patently offensive” speech on the internet that can be viewed by a minor.

However, that ruling left in place a provision deeming that sexually-oriented material that is “patently offensive under local community standards” is not protected by the First Amendment unless its author can prove its “redeeming social value.”

The NCSF challenged the CDA because it fears that personal websites and chat groups that include discussions and images of sadomasochism, swinging or polyamory are at risk of prosecution as a result of this provision. Membership groups that maintain educational websites about adult sexuality are also at risk, it says.

Since the CDA does not actually define the “local community standard” that would apply to the internet, the lawsuit claimed that the provision would give the most conservative communities in the country the power to dictate what all Americans read, write, and view on the internet.

Such uncertainty, the lawsuit claimed, creates a “chilling effect” on all internet content providers, including artists like Nitke, who must either resort to self-censorship or risk prosecution.

In their ruling, issued on Tuesday, three judges of the Federal District Court for the Southern District of New York agreed that NCSF members and Barbara Nitke are genuinely at risk of prosecution under the CDA and that their speech has in fact been inhibited.

But in order to succeed in their case, the NCSF and Nitke had to prove that the provision was not just too broad, but was substantially too broad.

The court noted that the relevant test for the "substantiality of overbreadth" has been established in previous cases: compare the amount of protected speech that is prohibited by the statute to the statute's "plainly legitimate sweep." So if the statute prohibits a substantial amount of speech relative to its legal breadth, the statute falls.

According to the Court, the NCSF and Nitke "have not established their claim that the overbreadth of the CDA, if any, is substantial and that the CDA therefore violates the First Amendment.”

John Wirenius, who represented the NCSF and Nitke in court, said:

"We are disappointed that the court did not act on the uncontradicted evidence we presented that artists and citizens who are sexual minorities are disproportionately censored by the Government's ability to pick its own forum and standard for obscenity cases. The government brings obscenity cases where it knows it can get convictions."

Barbara Nitke said she was "appalled" by the decision. "It is vitally important to keep the internet free for education, the arts and open discussion on sexual topics," she said. "This law is a form of unfair censorship that must be stopped. I am absolutely going to appeal this."

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