The question “What is a woman?” has become one of the most contentious debates in modern politics and culture. From transwomen winning women’s college championships in hurdles and swimming or being admitted into sororities, to conservative commentator Matt Walsh’s documentary What Is a Woman?, to U.S. Supreme Court Justice Ketanji Brown Jackson’s now-famous statement during her Senate confirmation hearings that she could not define the term because she is “not a biologist,” the definition of “woman” has shifted from a biological certainty to a source of international controversy. Once a straightforward classification, the term “woman” is now debated in contexts ranging from driver’s license designations and bathroom access to same-sex relationships and eligibility for women’s sports. This confusion reflects broader tensions over language, identity, and the role of objective reality in public policy.
In the United Kingdom, this definitional dispute recently reached the nation’s highest court. In 2018, a grassroots campaign group called For Women Scotland (FWS) formed to oppose the Scottish government’s move to allow individuals to legally self-identify their gender. FWS argued that redefining “woman” to include biological males weakened women’s legal rights and jeopardized safety in single-sex spaces. When the Scottish Parliament passed the Gender Recognition Reform Bill in 2022—making it easier to obtain Gender Recognition Certificates (GRCs)—FWS filed suit, and the case ultimately reached the UK Supreme Court.
On April 16, 2025, the Court issued a unanimous ruling: the terms “man,” “woman,” and “sex” in the UK’s Equality Act 2010 refer to biological sex, not gender identity—even for those with GRCs. The justices concluded that redefining these terms would undermine legal provisions related to pregnancy, maternity, and sexual orientation. While affirming that transgender individuals are protected under the category of “gender reassignment,” the Court drew a clear legal distinction between sex and gender identity. In short, under UK law, a woman is an adult human female.
The ruling had swift policy consequences. The Equality and Human Rights Commission (EHRC) issued guidance stating that transwomen—biological males who identify as women or girls—could be lawfully excluded from single-sex services, including women’s sports where safety or competitive fairness is at stake. This interpretation is consistent with the Equality Act’s allowance for sex-based separation in certain circumstances.
Major UK sports organizations quickly followed suit. The Football Association and Scottish FA banned transwomen from women’s competitions beginning in June 2025 and the 2025–26 season, respectively. The England and Wales Cricket Board adopted similar rules, and England Netball announced that only individuals of the female sex may compete in the women’s category as of September 1, 2025.
Though based on UK law, the ruling has international implications.
Global sports federations—such as World Aquatics (formerly FINA), World Athletics, and World Rugby—had already adopted eligibility criteria that exclude transwomen from elite female competition or require evidence of not having undergone male puberty. In the United States, similar developments have occurred in college sports. On April 8, 2024, the National Association of Intercollegiate Athletics (NAIA) announced a policy allowing only individuals who are female at birth to participate in women’s sports. On February 5, 2025, President Trump signed an executive order withholding federal funding from educational programs that allow males to compete in girls’ or women’s sports. The following day, the National Collegiate Athletic Association (NCAA) adopted a policy prohibiting male athletes from competing in women’s categories. The UK Supreme Court ruling strengthens the legal basis for such standards and may further influence policy in other jurisdictions.
The For Women Scotland decision offers a definitive legal answer to the question “What is a woman?”—at least within the UK. By reaffirming the legal primacy of biological sex, the ruling supports the efforts of sports organizations to preserve female categories for female bodies. For the United States and the broader international community, it serves as both a precedent and a philosophical touchstone in the ongoing effort to balance inclusion with safety and fairness.
As courts and policymakers around the world grapple with this issue, the UK Supreme Court’s decision is likely to shape the legal and cultural contours of the debate for years to come.
Follow Gregory Brown and For Women Scotland on X.
Image: “The Supreme Court of the United Kingdom” by Jay Galvin on Flickr
