The International Olympic Committee (IOC) has confirmed it is introducing a controversial new policy that will ban transgender athletes from competing in women’s events.The IOC stated eligibility for women’s events will be determined by a “once-in-a-lifetime” sex test, which would prevent transgender women and those with differences in sexual development from competing.It is an abrupt U-turn after the IOC previously left athletes’ eligibility up to their respective sports federations.Reactions to the decision were unsurprisingly fierce. From a legal point of view, it opens up a can of worms and will no doubt affect many athletes from the top level down to grassroots.What is the test?The IOC says “eligibility for the female category is to be determined in the first instance by SRY gene screening to detect the absence or presence of the SRY gene”.It added: Based on scientific evidence, the IOC considers the presence of the SRY gene is fixed throughout life and represents highly accurate evidence that an athlete has experienced male sex development. SRY stands for “sex determining region Y” gene. The presence of the SRY gene is associated with men’s typical sexual development. Read more: World Athletics’ mandatory genetic test for women athletes is misguided. I should know – I discovered the relevant gene in 1990 Any athlete whose test shows the presence of the SRY gene will be banned from the women’s category.The screening will be done via an athlete’s saliva, a cheek swab or blood sample.The IOC stated it is not retroactive and does not apply to any grassroots or recreational sports.Why did the IOC make this move?In September 2025 the IOC established a working group to examine scientific, medical and legal developments in this space. The IOC said the group reached a consensus that “male sex provides a performance advantage in all sports and events that rely on strength, power and endurance”.IOC president Kirsty Coventry said:At the Olympic Games, even the smallest margins can be the difference between victory and defeat. So, it is absolutely clear that it would not be fair for biological males to compete in the female category.The IOC added it had surveyed more than 1,100 Olympic athletes, which revealed “a strong consensus that fairness and safety in the female category required clear, science-based eligibility rules, and that protecting the female category is a common priority”.At the Tokyo Olympics in 2021, New Zealand weightlifter Laurel Hubbard became the first openly transgender woman to compete at an Olympic Games. She finished last in the super‑heavyweight category.The policy is widely expected to be adopted by individual sports federations, although many have already implemented similar testing in recent months, including World Athletics and World Aquatics.It will be implemented for women’s events at the Olympic Games, Youth Olympics and Games qualifiers, from Los Angeles 2028 onwards.Human rights law and sportThe IOC’s decision may be in opposition to several laws that aim to ensure everyone has the right to participate in sport.The United Nations’ International Charter of Physical Education and Sport states access to and participation in sport is an international human right. In 2019, a UN Human Rights Council resolution called on sports governing organisations such as the IOC to implement policies and practices that comply with international human rights.International human rights laws require countries protect and promote human rights. As many international sports governing organisations such as the IOC are based in Europe, the European Convention on Human Rights also applies to the new genetic testing rule. The IOC policy may violate this. The UN Human Rights Council states genetic sex testing as an eligibility requirement for women’s sport violates athletes’ international rights to equality, bodily and psychological integrity and privacy.While many support the IOC’s new policy, others argue the athletes now banned from competing in women’s sports are not being granted basic, long-agreed human rights.Affected athletes may challenge the new rules in the Court of Arbitration for Sport – world sport’s top court, which has in the past heard cases on gender eligibility.The IOC’s new rule may also violate the Council of Europe’s Convention on Human Rights and Biomedicine and domestic laws in many countries that prohibit genetic testing unless a health purpose is achieved. Those left on the sidelinesThis policy is a monumental shift from world sport’s most powerful authority.It has sparked celebration among some, and anger and disbelief among others.There will be aftershocks, maybe in the form of appeals or lawsuits. Where it leaves the few transgender and intersex athletes who want to compete in elite women’s sports is anyone’s guess.Matt Nichol does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.