London 2012: Marijuana expulsion for Olympic judo star Nick Delpopolo

Delpopolo, 23, who finished seventh in the 73kg event, issued an apology to the Olympic committee and to his fellow athletes.

The judoko said that he had not been smoking spliffs in the Olympic village but instead had mistakenly eaten a chocolate brownie that contained marijuana before he left New York for the London 2012 games.

"My positive test was caused by my inadvertent consumption of food that I did not realise had been baked with marijuana, before I left for the Olympic Games," said Delpopolo.

"I apologise to the U.S. Olympic Committee, to my team-mates, and to my fans, and I am embarrassed by this mistake. I look forward to representing my country in the future, and will re-dedicate myself to being the best judo athlete that I can be.”

The judo star is not asking for his case to be heard before the Disciplinary Commission and has said he understands his expulsion from the Olympics.

There have been calls for cannabis to be removed from the World Anti-Doping Agency's (WADA) prohibited list. President John Fahey indicated earlier this year that the organisation may look at changing the criteria for cannabis as a banned substance for athletes, however no decision is expected this year.

Substances make the banned list if they are proven to be performance enhancing, go against the spirit of sport or are dangerous to the health of athletes.

In the case of cannabis, it has not been suggested that the substance gives athletes a performance advantage in fast-paced sports, some experts say it could be helpful in sports like shooting or golf where a steady hand is required..