American athlete LaShawn Merritt has won his appeal against his Olympic ban after the doping law was overturned.

The 25-year-old, who currently holds the Olympic 400m title, was hit with a two-year suspension later brought down to 21 months after failing three drugs tests last year.

The International Olympic Committee rule 45 states that any athlete served with a ban lasting longer than six months cannot compete in the next Olympic Games.

Despite the ruling, Merritt appealed the decision on the basis that his suspension would need to amount to three years for him to miss the London 2012 Games, which breaches the World Anti-Doping Agency maximum ban of two years.

The outcome will allow the American to retain his 400m title in next year's London Olympics.