* U.S. judge rules against prosecutor in “sexting” case

* ACLU applauds decision

* Ruling may spur abuse of legal system - prosecutor

PHILADELPHIA, March 30 (Reuters) - A U.S. judge on Monday barred a Pennsylvania prosecutor from filing child pornography charges against three teenage girls caught with sexually suggestive pictures of themselves on their cell phones.

U.S. District Judge James Munley said he was issuing a restraining order on Wyoming County District Attorney George Skumanick because his proposed action would violate freedom of speech and parental rights.

The ruling came after the American Civil Liberties Union sued Skumanick on behalf of the girls and their families.

“The court agrees with the plaintiffs that the public interest would be served by issuing a TRO (temporary restraining order) in this matter as the public interest is on the side of protecting constitutional rights,” the judge said.

The case has attracted national attention and revolves around the growing practice among teens of “sexting,” a play on the term texting, in which nude or semi-nude photos are sent on cell phones or posted on the Internet.

The pictures, found last fall by officials of Pennsylvania’s Tunkhannock School District, showed two of the girls wearing bras, and another standing topless with a wrapped towel around her waist. No sexual activity was displayed.

Other unidentified people distributed the pictures.

Last month Skumanick told the girls and 17 other students that he would charge them with possessing or distributing child pornography, which is a felony, unless they agreed to probation and participated in a “re-education” program.

All but three agreed to his demands, setting the stage for the lawsuit.

Witold Walczack, legal director of the ACLU of Pennsylvania, welcomed the legal decision.

“This country needs to have a discussion about whether prosecuting minors as child pornographers for merely being impulsive and naive is the appropriate way to address the serious consequences that can result from sexting,” he said.

But Skumanick said it could encourage potential defendants to use the federal court system to evade state charges.

“My big fear is setting the precedent that would allow criminals in the state system seeking protecting in the federal system.” Skumanick said. When asked if he would appeal, he said was studying the opinion.

A national survey last fall found 20 percent of teenagers said they have sent or posted online nude or semi-nude pictures of themselves, and 39 percent said they have sent or posted sexually suggestive messages, according to the National Campaign to Prevent Teen and Unplanned Pregnancy. (Editing by Paul Simao)