The Court of Arbitration for Sport (CAS) cleared the way on Thursday for several dozen former doping offenders to compete at next year's Olympics after dismissing the validity of an International Olympic Committee (IOC) eligibility rule.
The controversial Rule 45, introduced in 2008, banned athletes, including Olympic 400 metres champion LaShawn Merritt, from participating at the next Olympic Games - summer or winter - if they have been suspended for six months or longer, but the regulation was rejected as invalid and unenforceable by CAS.
The Court's ruling means that American Merritt, the highest profile name affected by the decision, can now defend his title in London.
Merritt received a 21-month suspension after testing positive in 2009 and 2010 for a banned substance he said was found in an over-the-counter male enhancement product.
"We do not believe that the CAS decision will have any adverse impact on the anti-doping movement," said International Association of Athletics Federations (IAAF) spokesman Nick Davies.