What Does “Woman” Mean? A Legal Breakdown of the UKSC Ruling
In the case of For Women Scotland Ltd v The Scottish Ministers [2025] UKSC 16, decided in April 2025, the UK Supreme Court unanimously held that under the Equality Act 2010, "man", "woman", and "sex" refer to biological sex, meaning that "woman" refers to someone born female, not someone who has acquired a gender through a gender recognition certificate. The case invalidated guidance issued by the Scottish Government, which included trans women. The ruling will have effects in a variety of law and public policy areas.
The claim was started by For Women Scotland, an advocacy group that argued that the Scottish Government was exceeding its lawful authority by interpreting the language in the Equality Act definition to include trans women. The Scottish Government's guidance was intended to clarify who is counted as a "woman", in some provisions of the Act, which protect sex-based rights. The Scottish Courts had previously accepted that guidance. The Supreme Court, however, found the guidance inconsistent with the statute.
The Equality Act 2010 legislation does not use the terms "woman" or "man" in a biological or inclusive sense, but instead requires the courts to interpret the terms. The justices looked at the language as it was framed in 2010, the legislative history, and related provisions, for example, the Gender Recognition Act 2004. The justices concluded that Parliament was using "sex" and "woman" in a biological sense. They determined that merely recognizing acquired gender under the GRA did not change how "woman" appears in all parts of the Equality Act. One of the explanations the court provided is that to include "acquired gender" across the array of sex-based rights entails practical and legal difficulties. In some situations, whether or not to exclude people born female from protections intended for women may raise concerns about fairness or safety in single-sex spaces or services. The court suggested that unless Parliament chose to amend an Act of Parliament to redefine the terms, courts should assume the meaning Parliament intended in 2010.
This judgment clarifies that guidance from government cannot extend definitions beyond the definitions Parliament has legislated. Guidance from government is subordinate to statute. When guidance is inconsistent with the statute, courts may declare it invalid. The ruling is unequivocal that only Parliament can change key definitions.
The ruling demonstrates also how judicial interpretation shifts the framework of rights to achieve their end. Government policy, company policy, public services, and others who previously used the old guidance promised by government will have to look at them. In its instances where the guidance assumed trans women would be included in the definitions of "woman" for sex-based rights, those policies may be now unlawful under the ruling of the Supreme Court. Employers, service providers, charities will have to change.
The ruling has sparked political controversy. Supporters assert that it is clarifying - the law should be presumed to be understood in its original terms until Parliament changes the law. Critics argue that the ruling reduces protections for trans people, raises risk of exclusion, and may create greater potential for discriminatory policies. The ruling has also prompted questions about whether all corners of public law (including criminal justice, prisons, and medical treatment) will need a reinterpretation or a change to the legislation.
Its implications are broader than equality law. The decision raises issues of legal stability through clear definitions: when the words contained in statute are vague or ambiguous, courts will be required to choose one meaning over another. Meaning, how Parliament uses language in statute is significant, including what is not said. It also stresses the limits of guidance and policy: guidance cannot override or rewrite what is found in the statute.
The case also fits into the conversations of identity, rights and legislative competence in devolved governments. In Scotland, where some social policy is devolved, this makes clear that devolved administrations must interpret Acts of Parliament in the way Parliament intended. They cannot attach an assumption of broader inclusive definitions if there is no basis in legislation.
Legally, this ruling reinforces the principles of statutory interpretation. It confirms that when Parliament uses plain and ordinary words, the assumption will be courts typically hold the words to their ordinary meaning. It also reinforces the doctrine that rights and protections derive from enacted legislation and not from the aspiration of guidance or government policy without legislative change.
Furthermore, the ruling places pressure on future legislation. Any alterations in language used to define protection for protected classes will likely need explicit wording. There may be calls from Parliament to amend the Equality Act or pass new legislation clarifying these terms for inclusion or exclusion in the areas of sports, prisons, health services. For now, “woman” in the context of sex-based rights is, legally, biblically defined .
For those who are most concerned, there are consequences. Some trans women may be excluded from single-sex services, or single-sex space on the basis of the definition upheld by the ruling. Employers may be exposed to litigation risk, if they treat inclusive definitions inconsistent with the ruling, as lawful. Policies, and training materials may need revising. Institutions will need to check their practice is consistent with what the law now requires.
In addition to the ruling being consequential for those most concerned, the case gives citizens and campaigners a reminder, that law is made, not only from what is in legislation, but, importantly, from how courts deal with hard cases. Courts interpret statutes when the statutes cannot interpret themselves. Those interpretations then become the basis for the enforcement of law. It matters that lawyers, policy makers and campaigners watch what definitions meant, in practice. Language in law is powerful. Words matter.
The question “What does law define when it says ‘woman’?” has a definitive legal answer in this case. Under the Equality Act 2010 in the UK, “woman”, “man” and “sex” mean biologically defined sex. The law provides some means for trans people to be protected under a provision set out in another part of the statute, however, where the statute uses those key terms, without qualification, we know the meaning is as Parliament set them in 2010.
The Supreme Court ruling illustrates that law isn’t static. Even where definitions are settled and established, they can still be challenged. Cases such as this change the way law makes it way in real live. They change policy; they change public bodies’ practice; and they show that courts can make justice and governance work with equal reliance, or authority, and clarity and ethics, as well as political will.
