The UK Supreme Court: The legal definition of "woman" is based on biological sex

In a landmark ruling handed down on April 16, 2025, the UK Supreme Court has unanimously determined that the terms ‘woman’ and ‘sex’ in the Equality Act 2010 refer exclusively to biological sex. This means that ‘women’ and ‘sex’ in the Equality Act are defined on a biological basis, i.e. being born female of the human species.

According to the Supreme Court ruling, the issue at issue in the appeal from which it arose was to give a legal interpretation of the meaning of ‘man’, ‘woman’ and ‘sex’ in light of the Equality Act 2010 (“EA 2010”). This ruling follows a protracted legal battle brought by the feminist organization For Women Scotland (FWS) against the Scottish Government, which had sought to broaden the definition of ‘woman’ in the legislation on gender representation on Public Boards to include self-identified males with Gender Recognition Certificates (GRCs) and to encourage their increased political participation on such boards. The challenged legislation was held to be unlawful by the lower court (Inner House), which found that the statutory definition usurped matters outside the legislative competence of the Scottish Parliament.

In its ruling, the Supreme Court interprets the legal definition of 'sex' on a biological basis, i.e. that sex is determined by biology and not by gender, or in other words, by the roles and stereotypes with which people identify, which is the criterion on which transgenderism is based. This means that, in light of material reality, and the Supreme Court's interpretation of the law, women are only those born female. Therefore, in the Supreme Court's ruling, the legal definition of 'woman' implies the exclusion of self-identified males, even those who possess a GRC, that is, those who have requested and obtained the misnamed change of the registered sex.

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