A judge has explained his decision to quash convictions against a Missouri mother for her role in an internet hoax directed at a 13-year-old neighbour who later committed suicide.
US District Judge George Wu said in his written ruling that the case, billed as America's first cyberbullying trial, was never a legal test of such crimes.
Prosecutors, who adopted that terminology early on, brought charges against Lori Drew under the Federal Computer Fraud and Abuse Statute which did not involve cyberbullying, the judge said.
Judge Wu acquitted Drew last month of misdemeanour counts of accessing computers without authorisation, but had stressed the ruling was tentative until he issued it in writing.
Drew's lawyer, Dean Steward, said Judge Wu's ruling effectively stuck down a portion of the computer fraud act.
"He's pretty much found that portions of it are unconstitutional," said Mr Steward, who expects Department of Justice lawyers to go back to Congress for clarification.
Thom Mrozek, spokesman for the US attorney's office in Los Angeles, said no decision had been made yet about a possible appeal.
Prosecutors said Drew sought to humiliate Megan Meier by helping create a fictitious teenage boy on the MySpace social networking site and sending flirtatious messages to the girl in his name.
The fake boy then dumped Megan in a message saying the world would be better without her. Megan hanged herself a short time later, in October 2006, in Missouri.
Drew was not directly charged with causing Megan's death, but prosecutors indicted her under the computer fraud act, which in the past has been used in hacking and trademark theft cases.
Judge Wu's 32-page ruling cited vagueness of the statute and the chance that innocent users of the internet could become subject to criminal charges if Drew's conviction was allowed to stand.
He gave examples of people who could be liable for breaking MySpace rules online including "the lonely-heart who submits intentionally inaccurate data about his or her age, height and/or physical appearance", or "the exasperated parent who sends out a group message to neighbourhood friends entreating them to purchase his or her daughter's Girl Scout cookies", a breach of rules against advertising or soliciting sales.