ATLANTA — A judge yesterday voided a 10-year sentence for a man accused of having consensual oral sex with a 15-year-old girl when he was 17. He instead gave Genarlow Wilson a 12-month misdemeanor sentence with credit for time already served.

The state is likely to appeal the ruling.

Mr. Wilson’s original sentence, for aggravated child molestation, was widely criticized on the grounds it was grossly disproportionate to the crime, and state lawmakers later passed a law to close the loophole that led to the 10-year sentence.

Mr. Wilson, now 21, has already served more than 27 months. He could remain behind bars while the appeal proceeds.

A jury found the honor student guilty in 2005 of aggravated child molestation for having oral sex with a 15-year-old girl during a 2003 New Year’s Eve party involving alcohol and marijuana. Although the sex act was consensual it was illegal under Georgia law.

Mr. Wilson was also charged with rape for being one of several male partygoers at the Douglas County hotel to have sex with a 17-year-old girl, but he was acquitted. The party was captured on a videotape that was played for the jury.

Several influential people, including President Carter, stepped forward to support Mr. Wilson.

Mr. Wilson’s lawyers could be heard applauding in their office after the order was released.