In April 2018, the IAAF announced new "differences of sex development" rules that required athletes with specific disorders of sex development, testosterone levels of 5 nmol/L and above, and certain androgen sensitivity to take medication to lower their testosterone levels, effective beginning 8 May 2019. Due to the narrow scope of the changes, which also apply to only those athletes competing in the 400m, 800m, and 1500m, many people thought the rule change was designed specifically to target Caster Semenya, the multiple time Olympic and World Champion at 800 metres. On 19 June 2018, Semenya announced that she would legally challenge the IAAF rules. On 1 May 2019, the Court of Arbitration for Sport rejected her challenge, paving the way for the new rules to come into effect on 8 May 2019. During the legal challenge by Semenya, the IAAF amended the regulations to exclude hyperandrogenism associated with the 46, XX karyotype and clarified that the disorders of sex development affected by the regulations are specific to the 46, XY karyotype. The legal case divided commentators such as Doriane Coleman, who testified for the IAAF, arguing that women's sport requires certain biological traits, from commentators such as Eric Vilain, who testified for Semenya, arguing that "sex is not defined by one particular parameter... for many human reasons, it's so difficult to exclude women who've always lived their entire lives as women — to suddenly tell them 'you just don't belong here.'" Semenya has appealed the decision to the Federal Supreme Court of Switzerland. On 3 June 2019, the Swiss Federal Supreme Court advised that they had "super-provisionally instructed the IAAF to suspend the application of the 'Eligibility Regulations for the Female Classification for athletes with differences of sex development' with respect to the claimant " until the court decides whether to issue an interlocutory injunction. On July 30, 2019 the Swiss Federal Supreme Court reversed its earlier ruling that had suspended the Court of Arbitration for Sport decision and the IAAF rules. For that reason, Semenya, silver medalistFrancine Niyonsaba and Olympic bronze medalist Margaret Wambui missed the 2019 World Athletics Championships in Doha in October 2019, while continuing legal appeals. The number 3 400 meter runner for 2019, Aminatou Seyni had to switch events to a weaker event, the 200 metres, in order to adhere to this rule. In July 2019, Semenya said that the ongoing issue has "destroyed" her "mentally and physically".
