## Facts

- In 2018, the International Association of Athletics Federations (IAAF) adopted Eligibility Regulations for the Female Classification for athletes with certain differences of sex development (DSD).
- The regulations applied to athletes recognized as female who have specified 46 XY DSD conditions and endogenous testosterone above 5 nmol/L, in certain “Restricted Events” (including 400m, 800m, 1500m, and the mile) at international competitions.
- To compete in the female category in Restricted Events, covered athletes had to reduce testosterone below 5 nmol/L, maintain it for at least six months, and continue to maintain it thereafter, typically through hormonal treatment and monitoring.
- Mokgadi Caster Semenya and Athletics South Africa (ASA) filed CAS arbitration challenging the regulations under the IAAF Constitution, the Olympic Charter, Monaco law, and generally recognized human-rights norms.
- The cases were heard together after a multi-day evidentiary hearing in February 2019.
- A three-member CAS panel issued an award on April 30, 2019, dismissing the claims by a 2–1 vote.

## Issues

1. Whether the DSD Regulations discriminate on prohibited grounds (including sex and sex characteristics) under the applicable governance and legal framework.
2. If discriminatory, whether the discrimination is justified as necessary, reasonable, and proportionate to the legitimate objective of protecting fair competition in the female category for the Restricted Events.
3. Whether the scientific record sufficiently supports the design choices (event scope, 5 nmol/L threshold, and required medical intervention and monitoring), or instead renders the regulations arbitrary or disproportionate.

## Decision

- The panel held that the DSD Regulations are discriminatory because they impose eligibility conditions on a defined subset of women based on sex-linked biological traits.
- By majority, the panel found the discrimination justified as a necessary, reasonable, and proportionate means of achieving a legitimate objective: ensuring fair competition in the female category in the Restricted Events.
- The panel accepted that endogenous testosterone is a primary factor associated with the male–female performance gap and found sufficient evidence that elevated testosterone in covered 46 XY DSD athletes yields a significant competitive advantage in the Restricted Events.
- The panel concluded that lowering testosterone to the specified level was rationally connected to reducing the advantage and that no equally effective, less restrictive alternative had been shown on the record.
- The panel acknowledged serious concerns about implementation (privacy, investigative practices, stigma, and medical risks), but held those concerns did not, on the evidence presented, negate proportionality; it signaled that future experience and evolving science could alter the assessment.
- The requests for arbitration were dismissed, and the DSD Regulations were upheld as valid as drafted at the time.

## Legal Principles

- Sports eligibility rules may differentiate among athletes; when differentiation is discriminatory, it can be lawful if it pursues a legitimate aim and is necessary, reasonable, and proportionate.
- Preserving meaningful fair competition in a protected women’s category may qualify as a legitimate objective capable of justifying differential eligibility conditions.
- Proportionality analysis commonly evaluates (1) rational connection between the measure and the objective, (2) necessity in light of less restrictive alternatives, and (3) overall balance between burdens imposed and the importance of the objective.
- Where a rule requires medical intervention and ongoing monitoring, proportionality must account for bodily integrity impacts, health risks, privacy intrusion, and stigma, alongside competitive fairness considerations.
- Findings of proportionality may be contingent where the scientific evidentiary base is contested or incomplete and where practical application may materially affect the rule’s justification over time.

## Conclusion

CAS upheld the IAAF DSD Regulations despite finding them discriminatory, concluding that, on the record presented, they were a justified and proportionate means of protecting fair competition in specified women’s track events, while warning that implementation and evolving evidence could require reassessment.


Semenya v. Int'l Ass'n of Athletics Federations, CAS 2018/O/5794 (Ct. Arb. Sport 2019)