Updated

The highest court in sports has overturned a disputed IOC doping rule, clearing the way for reigning Olympic 400-meter champion LaShawn Merritt to defend his title at next year's London Games, officials with knowledge of the decision told The Associated Press on Thursday.

The Court of Arbitration for Sport invalidated the International Olympic Committee rule that bars any athlete who has received a doping suspension of more than six months from competing in the next summer or winter games, half a dozen officials informed of the decision told the AP.

They spoke on condition of anonymity because the decision hadn't been officially announced by CAS in Lausanne, Switzerland.

The case centered on Merritt, the American 400-meter gold medalist in Beijing who had been ineligible under the IOC rule to compete in London even though he completed his doping ban earlier this year.

The U.S. Olympic Committee challenged the rule, contending it amounts to a second penalty for a single offense and violates global anti-doping guidelines. The IOC maintained it was a question of eligibility, not a sanction, and the Olympic body had the right to decide who takes part in its events.

The USOC and IOC went to CAS to seek a ruling well ahead of the London Games to avoid last-minute confusion before the Olympics start on July 27, 2012.

An eight-hour hearing was held in Lausanne on Aug. 17.

The CAS decision means Merritt becomes eligible to compete in London, as will any other athletes around the world who have been affected by the rule.

The verdict against the IOC also opens the door for athletes in Britain to challenge a British Olympic Association rule that bans drug offenders for life from the games.

Among those affected by the British ban are sprinter Dwain Chambers, a former European 100-meter champion who served a two-year ban in the BALCO scandal, and cyclist David Millar, who also was suspended for two years for use of EPO.

The IOC's rule -- known as Rule 45 -- took effect in 2008, just ahead of the Beijing Games, but London would have been the first Summer Olympics fully covered by it.

Merritt, who was also 400-meter world champion in 2009, received a 21-month suspension last year after testing positive for a banned substance found in a male-enhancement product.

His penalty was reduced from the usual two-year suspension because he cooperated with authorities and was found to not have taken the drug to enhance athletic performance.

Merritt's ban expired in July and he returned to international competition, including the world championships in Daegu, South Korea. He finished second in the 400, overtaken down the stretch by Kirani James of Grenada, but helped the Americans win gold in the 4x400 relay.

The American Arbitration Association panel, which banned Merritt, said the IOC rule went against the World Anti-Doping Agency code and would essentially extend his ban to three years.