A judge in New York has dismissed a teen's defamation lawsuit against Facebook, ruling that the site isn't responsible for false posts by users.

"Facebook is entitled to the liability shield conferred by the Communications Decency Act," wrote New York County Supreme Court Judge Debra James. That law says that Web sites are immune from defamation lawsuits based on user-generated content.

The teen, Denise Finkel, had brought a $3 million defamation lawsuit against Facebook as well as four former high school classmates who allegedly harassed her on the site. She alleged in her lawsuit, filed in March, that the other students created a Facebook group called "90 Cents Short Of A Dollar" to taunt her. The students allegedly posted false remarks indicating that Finkel "was a woman of dubious morals, dubious sexual character" and that she "engaged in bestiality," was "an IV drug user" and had contracted AIDS.

The case against Facebook was widely viewed as unlikely to succeed because of the federal Communications Decency Act. Eric Goldman, director of the High Tech Law Institute at Santa Clara University, said back in March that Facebook was "categorically immune" from defamation lawsuits. "It was a bad call by the plaintiff to sue them at all, and frankly, it detracts from their otherwise serious allegations," he said at the time.

Finkel attempted to argue that Facebook wasn't the type of Web site that could claim immunity under the Communications Decency Act, on the theory that Facebook asserted in its terms of service that it owned users' content. (Facebook later revised those terms to clarify that users own their content.)

But James rejected that theory, ruling that ownership of content was irrelevant. She quietly threw out the case last month.

Facebook not only argued that the case should be dismissed, but also sought sanctions against Finkel and her attorney for having filed it. James rejected that portion of Facebook's request, ruling that the lawsuit wasn't clearly frivolous.

Finkel's lawyer, Mark Altschul, says his client doesn't intend to appeal and will proceed with the case against her former classmates. "Despite my opinion that the case would have been won on appeal, my client did not seek or enjoy the media attention," Altschul said. "She felt that further litigation against Facebook would bring more attention to her than she wished."

Facebook praised the ruling in a statement. "We're pleased the courts continue to confirm that just as phone companies, email providers and postal services are not liable for misuse of their services to send inappropriate content, neither is Facebook," the company said.

The company also said that it intends to seek sanctions in future lawsuits based on user-generated content. "These cases are dismissed time and again," the company said. "We think they should stop and that there should be penalties for wasting the court's time."