ATLANTA — Georgia’s Supreme Court today ordered the release of a young man who has been imprisoned for more than two years for having consensual oral sex with another teenager.

The court ruled 4-3 that Genarlow Wilson’s 10-year sentence was cruel and unusual punishment.

Wilson’s lawyer, B.J. Bernstein, said she expected Wilson would be released this afternoon from the Al Burruss Correctional Training Center in Forsyth, Ga.

“His mother is just thrilled. We’re all in a little bit of shock,” Mr. Bernstein said.

Wilson, 21, was convicted of aggravated child molestation following a 2003 New Year’s Eve party at a Douglas County hotel room where he was videotaped having oral sex with a 15-year-old girl. He was 17 at the time.

Wilson was acquitted of raping another 17-year-old girl at the party.

The 1995 law Wilson violated was changed in 2006 to make oral sex between teenagers close in age a misdemeanor, similar to the law regarding teenager sexual intercourse. But the state Supreme Court later upheld a lower court’s ruling which said that the 2006 law could not be applied retroactively.

Chief Justice Leah Ward Sears wrote in the majority opinion that the changes in the law “represent a seismic shift in the legislature’s view of the gravity of oral sex between two willing teenage participants.”

Judge Sears wrote that the severe punishment makes “no measurable contribution to acceptable goals of punishment” and that Wilson’s crime did not rise to the “level of adults who prey on children.”

State Attorney General Thurbert Baker said he accepts today’s ruling.

Mr. Baker said he hopes the ruling will “put an end to this issue as a matter of contention in the hearts and minds of concerned Georgians and others across the country who have taken such a strong interest in this case.”

Wilson’s supporters were jubilant.

“It’s been a long time coming,” U.S. Rep. John Lewis, an Atlanta Democrat, said. “Each day that this young man spent in prison was a day too long.”

A civil rights activist, Jesse Jackson, who is visiting Georgia this week, called for an end to mandatory minimum prison sentences.

State lawmakers announced they had raised $4,000 toward a scholarship fund for Wilson, and Mr. Jackson promised another $5,000 from the Rainbow/PUSH organization.

The state Supreme Court had turned down Wilson’s appeal of his conviction and sentence, but the justices agreed to hear the state’s appeal of a Monroe County judge’s decision to reduce Wilson’s sentence to 12 months and free him. That judge had called the 10-year sentence a “grave miscarriage of justice.”

Dissenting justices wrote that the state Legislature expressly stated that the 2006 change in the law was not intended to affect any crime prior to that date.

They said Wilson’s sentence could not be cruel and unusual because the state Legislature decided that Wilson could not benefit from subsequent laws reducing the severity of the crime from a felony to a misdemeanor.

They called the decision an “unprecedented disregard for the General Assembly’s constitutional authority.”