Last month, the Court of Arbitration for Sport ("CAS") ruled against Caster Semenya in her long-standing dispute with the International Association of Athletics Federation ("IAAF"). The decision means Semenya has no choice but to lower her testosterone level in order to compete in international mid-distance events.

The athlete had challenged IAAF's introduction of new eligibility regulations for female classification, ("regulations"), which govern the admissibility in several events of female athletes with certain disorders of sexual development ("restricted DSDs"). Those who fell within the regulations' scope would not be permitted to compete internationally in mid-distance events (in which Semenya frequently competes). A female athlete would fall within this scope if, amongst other criterion, their testosterone measured at 5nmol/L or above (the average level for women without DSDs being between 0.7-2.8nmol/L). Under the regulations, if that athlete's body can 'make use' of the higher testosterone level present, they will only be allowed to compete in these restricted events if they lower their testosterone to below 5nmol/L, and keep it below this level.

Semenya argued that the regulations discriminated unfairly, lacked a concrete scientific basis, and posed a risk to the health of those athletes affected. On the evidence presented to it, CAS ruled that the regulations were discriminatory, however, the discrimination was necessary and proportionate to guarantee fairness in female athletics. In its reasoning, CAS stated that the male/female divide in athletics was not there to protect women from having to compete against men because men have an advantage over them, but to protect athletes who do not possess certain advantages having to compete against other athletes  who do (in this case the advantage being higher levels of testosterone).

This ruling has frustrated many and raises several concerns, some of which CAS itself admitted would subsequently need to be addressed. There is the question of potential side effects that may arise from using hormonal treatment to lower testosterone, and what is to happen if these start affecting an athlete's ability to perform at their best. Many have made the point that requiring individuals to physically modify themselves in order to be allowed to do something is worryingly unethical. CAS stated that further research into hormonal treatment may "demonstrate the practical impossibility of compliance which could, in turn, lead to a different conclusion as to the proportionality of the DSD regulations." The Court also ruled that further research is needed to prove that athletes with restricted DSDs do actually have an advantage in 1,500m and 1 mile events (both of which come under the regulations' restricted events), as the current evidence is not enough to substantiate this claim.

There is also the question of how to go about merging (or replacing) the traditional male and female categories in sport with the fact that an athlete's sex might no longer simply be able to be placed into one of these. Will these traditional categories remain? Or do we need to create more based on athletes' testosterone levels? The necessity to address (and find an answer to) this reality will only increase with time, and how to go about doing this on an ethical, social and biological level may prove to be difficult.

It will always be a complex line to tread between protecting athletes by ensuring they have a fair chance to compete on a level playing field, and protecting them against unfair discrimination which could potentially cost them their career. As CAS made clear in its ruling, it remains to be seen if the regulations can be enforced fairly, and further research is needed in order to determine this. It is likely that Semenya (with a lot of support behind her) will appeal CAS's ruling, so this landmark case may not be over just yet.

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