|World Champion Merritt (R) will be able to take on rivals such as Kirani James (L) again in London [GALLO/GETTY]
Olympic champion LaShawn Merritt is free to defend his 400m title in London next year after the American won his appeal on Thursday against an IOC rule banning doping offenders from the games.
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.
The three-man CAS panel said the rule, adopted in 2008, was "invalid and unenforceable" because it amounted to a second sanction and did not comply with the World Anti-Doping Agency code.
It said the rule amounted to a "disciplinary sanction" rather than a matter of eligibility.
Merritt, the American 400-meter gold medalist in Beijing, had been ineligible under the IOC rule to compete in London even though he completed his doping ban earlier this year after testing positive for a banned substance found in a male-enhancement product.
The U.S. Olympic Committee challenged the rule and was backed by several other national Olympic and anti-doping bodies. The IOC maintained it had the right to decide who is eligible to take part in its games.
The IOC said on Thursday it "fully respects" the CAS verdict and will comply with it. However, the IOC said it would push for the rule to be included in a revised WADA code in 2013.
The CAS decision means Merritt becomes eligible to compete in London, as do other athletes around the world who have been affected by the rule.
"We're obviously happy about that,'' said USOC CEO Scott Blackmun.
"LaShawn made an error that he even admitted was a silly error. We're glad he's going to be able to compete."
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 100m 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 ruling means other banned athletes such as Dwain Chambers could compete at Olympics [GETTY]
"The IOC has a zero tolerance against doping and has shown and continues to show its determination to catch cheats," the IOC said in a statement.
"We are therefore naturally disappointed since the measure was originally adopted to support the values that underpin the Olympic Movement and to protect the huge majority of athletes who compete fairly.
"The rule was in our view an efficient means to advance the fight against doping, and we were somewhat surprised by the judgment since we had taken an advisory opinion from CAS on the rule and been given a positive response."
CAS, which is based in Lausanne, Switzerland, said the IOC could propose an amendment to the WADA code that would mean the rule would be "part of a single sanction."
"When the moment comes for the revision of the World Anti-Doping Code we will ensure that tougher sanctions, including such a rule, will be seriously considered," the IOC said in its statement.
Blackmun thanked the IOC for agreeing to take part in the arbitration.
"We completely support the IOC in their efforts to have stringent anti-doping sanctions," he said.
"t's just that this case created uncertainty for our athletes. This was a mutual decision to get some clarity."
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 August 17.
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.