Caster Semenya - testosterone, sex, and a question of proportionality

Africa, Switzerland, UK

On Monday 3 June 2019, the Federal Supreme Court of Switzerland provisionally suspended the application of new rules which would have required South African runner Caster Semenya to reduce her blood testosterone level in order to compete in certain athletics events.

The rules in question (the Eligibility Regulations for the Female Classification (Athletes with Differences of Sex Development (“DSD Regulations”)), were enacted by the International Association of Athletics Federations (“IAAF”) in April 2018 with the stated aim “to ensure fair and meaningful competition within the female classification, for the benefit of the broad class of female athletes”.

The decision of the Federal Supreme Court of Switzerland to suspend the application of the DSD Regulations followed the controversial and widely publicised decision of the Court of Arbitration of Sport (“CAS”), made on 30 April 2019, to dismiss requests for arbitration made by Ms Semenya and Athletics South Africa in relation to the DSD Regulations. In its decision, the CAS found that the DSD Regulations are discriminatory, but that such discrimination is a “necessary, reasonable and proportionate means of achieving the legitimate objective of ensuring fair competition in female athletics in certain events”.

UK approach

The justification of apparent discrimination presents complex legal and ethical questions. The role of the CAS in determining whether a form of discrimination can be justified draws comparison to the role UK employment tribunals play in determining whether some forms of workplace discrimination can be objectively justified.

It is important to note that were the CAS to have applied the law of England and Wales (or Scotland) in Ms Semenya’s case, the outcome may have been different. The DSD Regulations are, on the face of it, directly sex discriminatory as they apply only to a specific subset of female athletes. Despite this, the CAS ruled that they could be justified. This is different to the UK approach as, under the Equality Act 2010 (“EqA”), direct sex discrimination cannot be objectively justified. The UK approach to this complex case may also differ in light of a specific exclusion contained in the EqA, which applies to “gender-affected” sports. This exclusion may be wide enough to permit the discriminatory effect of the DSD Regulations.

Discrimination in the workplace

In a UK employment context, an employer may avoid liability for apparent indirect discrimination, if it can demonstrate that its actions were a proportionate means of achieving a legitimate aim. It is this test, in particular the proportionality element of it, which draws comparison to the decision of the CAS in the Semenya case.


In assessing proportionality, a UK employment tribunal will conduct a balancing exercise, involving evaluation of the discriminatory effect of a provision, criteria or practice (“PCP”) against the reason an employer applied such a PCP, taking into account all the relevant facts.

In the Semenya case, the CAS had the unenviable task of determining whether the DSD Regulations were proportionate. Whilst the full 165-page award has not been published, the executive summary of the award indicates a similar balancing exercise had to be conducted in assessing whether discriminatory DSD Regulations could be deemed proportionate.

Despite reaching a conclusion that the DSD Regulations are proportionate, the CAS recognised “serious concerns about aspects of the practical application of the DSD Regulations” as well as a “paucity of evidence to justify the inclusion of two events (the 1500m and one mile events)” within the restricted categories of events to which the DSD Regulations apply. This open recognition points to the challenges of this case. To reach a conclusion that an action or regulation is proportionate, it is necessary to have a sufficient understanding of its effect but also to assess whether there is a less discriminatory means of achieving the legitimate aim. This is clearly problematic, as there is currently a limited understanding of the effects of the hormonal treatment required to reduce an athlete’s level of testosterone.

From a proportionality perspective, it is also difficult to objectively justify the application of the DSD Regulations to 1500m and 1 mile races. This is due, as acknowledged by the CAS, to the lack of concrete evidence to demonstrate that the sub-set of athletes caught by the DSD Regulations (including Ms Semenya) have a significant athletic advantage in such races.

Because of these issues, there is a cogent argument that the DSD Regulations cannot be proportionate, as there is not enough data to justify their implementation. In the short to medium term, it is difficult to see how this position will change.


The case of Ms Semenya highlights the difficulties faced in the detailed application of discrimination legislation, in particular in what circumstances should discrimination be deemed lawful. The difficulties faced by the CAS were therefore analogous to the work of UK employment tribunals.

The case has also brought to the fore a complex challenge to the binary male / female classification within sports. Such a challenge is facilitated by improvements in our understanding of physiology and performance.

The final outcome of proceedings in the Swiss courts (following the provisional suspension of the DSD Regulations by the Federal Supreme Court of Switzerland) remains to be seen. However, it may be that the IAAF’s justifiable attempt to ensure fair competition in female athletics is undone by the current limit to our understanding of physiology.

Yet another interesting dimension to this case is the application of human rights law. At the CAS, Ms Semenya’s legal team sought to challenge the DSD Regulations on the basis they violated universally recognised fundamental human rights. This aspect of Ms Semenya’s legal challenge may, if rejected by the Swiss courts, result in proceedings before the European Court of Human Rights.

It is likely that the Semenya case will continue to cause controversy for some time. However, in an era of increasingly polarised public debate, the CAS rightfully noted that, in this case, there are issues in play upon which reasonable and informed minds may legitimately differ.