In For Women Scotland Ltd. v. The Scottish Ministers, (UK SC, April 16, 2025), the United Kingdom Supreme Court held that considering the interaction of the Gender Recognition Act 2004 with the Equality Act 2010, the terms "woman", "man", and "sex" in the Equality Act refer to biological sex. The Equality Act gives separate protection to persons who have undergone or are proposing to undergo sexual reassignment. The court explains the limited question it is deciding:
24. ... [A] person who is aged at least 18 can apply for a GRC [Gender Reassignment Certificate] under the GRA 2004. Section 9(1) of that Act provides that when a full GRC is issued to a person the person’s gender becomes “for all purposes” the acquired gender so that if the acquired gender is the female gender, the person’s sex becomes that of a woman....
25. The central issue on this appeal is whether references in the EA 2010 to a person’s “sex” and to “woman” and “female” are to be interpreted in the light of section 9 of the GRA 2004 as including persons who have an acquired gender through the possession of a GRC.
26. The focus of this appeal is not on the status of the large majority of trans people who do not possess a full GRC. Their sex remains in law their biological sex. This appeal addresses the position of the small minority of trans people who possess a full GRC....
The court summarized its ruling in part as follows:
265.... (xii) Gender reassignment and sex are separate bases for discrimination and inequality. The interpretation favoured by the EHRC and the Scottish Ministers would create two sub-groups within those who share the protected characteristic of gender reassignment, giving trans persons who possess a GRC [Gender Reassignment Certificate] greater right than those who do not. Those seeking to perform their obligations under the Act would have no obvious means of distinguishing between the two sub-groups to whom different duties were owed, particularly since they could not ask persons whether they had obtained a GRC....
(xiii) That interpretation would also seriously weaken the protections given to those with the protected characteristic of sexual orientation for example by interfering with their ability to have lesbian-only spaces and associations....
(xiv) There are other provisions whose proper functioning requires a biological interpretation of “sex”. These include separate spaces and single-sex services (including changing rooms, hostels and medical services), communal accommodation and others....
(xv) Similar incoherence and impracticability arise in the operations of provisions relating to single-sex characteristic associations and charities, women’s fair participation in sport, the operation of the public sector equality duty, and the armed forces....
The UK Supreme Court also issued a 4-page Press Summary of the Court's 88-page Opinion. And CBS News reports on the decision.