American sprinter Sha’Carri Richardson’s one-month ban on Friday after her positive test for cannabis has reignited the debate about the logic behind the drug’s inclusion on the World Anti-Doping Agency’s (WADA) banned list.

Richardson was among the favourites to win gold in the 100 metres at this year’s Tokyo Olympics but her positive test for a banned substance, which the 21-year-old said she used to deal with the death of her mother, crushed those dreams.

Her suspension, which leaves open the possibility that she could still compete in the women’s 4x100m relay event in Tokyo, comes as the legalisation of adult recreational use of marijuana is spreading around the United States.

However, Olympic athletes must adhere to a different set of rules, even if few experts think marijuana, or cannabis, can do much to enhance the kind of speed, strength, power or precision that Olympic athletes strive for.

“There exists no scientific consensus that the acute effects of marijuana enhance athletic performance,” said Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws.

Richardson’s period of ineligibility, which began on June 28, was reduced to a month because her use of cannabis occurred out of competition and was unrelated to sport performance.

“The rules are clear, but this is heartbreaking on many levels,” said United States Anti-Doping Agency Chief Executive Travis Tygart.

“Hopefully, her acceptance of responsibility and apology will be an important example to us all that we can successfully overcome our regrettable decisions, despite the costly consequences of this one to her.”

Arbitrary rules

The World Anti-Doping Agency (WADA), as part of a policy change this year, has reduced its ban for recreational drugs so that athletes who test positive out of competition would be banned for one to three months instead of two years.

According to WADA, for a substance to be on its prohibited list it must meet any two of the following criteria: performance enhancement, danger to an athlete’s health and violation of the spirit of sport.

Calls to remove marijuana from WADA’s list of in-competition banned substances have become more frequent and many athletes and experts have openly advocated for legalisation.

“She was suspended because of arbitrary rules,” Carl Hart, a Columbia University psychology professor, said of Richardson’s ban before discussing how marijuana is legally accepted in a growing number of U.S. states and around the world.

“These liberalising laws are highlighting the arbitrariness of our cannabis laws and the stupidity of them. This (ban) further shows the hypocrisy.”

The heart of the problem is where to draw the line between performance-enhancing drugs - which many experts agree should be prohibited in sports because they make the contest unfair - and recreational drugs, which have little bearing on performance but could give sport a bad image.

“I don’t know why marijuana is banned. Maybe a good reason. Maybe not. I know how it feels to lose a parent. Indescribable pain!,” retired American sprinter Michael Johnson, a four-time Olympic gold medallist, said on Twitter.

“I’m from the same neighbourhood as (Sha’Carri) Tough place! I wish people would stop calling her and this ban stupid unless you know the reason for both.”