Supreme Court ruling on the legal definition of a "woman": considerations for employers

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25.04.2025

In a significant ruling, the Supreme Court has unanimously confirmed that the definitions of “woman”, “man” and “sex” for the purposes of the Equality Act 2010 (EA 2010) refer to biological sex.

In this blog, we explain the Supreme Court’s decision and highlight potential considerations for employers arising from the judgment and the Equality and Human Rights Commission’s interim update.

Background to the case

The case of For Women Scotland Ltd v The Scottish Ministers originated as a dispute about the interpretation of "woman" in the Gender Representation on Public Boards (Scotland) Act 2018. This legislation created gender targets to increase the proportion of women on public boards in Scotland. The Scottish Government proposed including anyone with a Gender Recognition Certificate (GRC) recognising their gender as female in the definition of “woman” for these targets. A GRC is a document that allows someone to change their gender legally.

The campaign group For Women Scotland (FWS) brought a case challenging this interpretation. It argued instead that the definition of a “woman” under the EA 2010 (and by extension, the Scottish legislation) refers to biological sex and that a trans woman with a GRC remains biologically male.

This argument was rejected by the Scottish Courts and FWS appealed to the Supreme Court. The central question before the Supreme Court was whether the term “sex” under the EA 2010 refers solely to “biological sex” (the sex of a person at birth) or includes “certified sex” (someone’s gender acquired under a GRC).

The Supreme Court’s judgment

The Supreme Court confirmed unanimously that the definition of “woman” for the purposes of the EA 2010 is limited to biological, rather than certified, sex.

The Court’s main reasons for this are that:

There “can be no doubt” that when drafting the Sex Discrimination Act 1975 – on which the EA 2010 was based – Parliament intended the definitions of “man” and “woman” to refer to biological sex. The EA 2010 also makes it clear that the concept of sex is binary and based on biological characteristics.
Protection for trans people under the EA 2010 is based on the protected characteristic of gender reassignment, which is defined distinctly from sex and provides separate protections.
It is possible to disapply legislation on GRCs (under which a person with a GRC becomes their acquired gender) if it would make other legislative provisions incoherent or unworkable. As a matter of ordinary language, the provisions relating to sex discrimination in the EA 2010 “can only be interpreted as referring to biological sex”. Any other interpretation would render provisions, such as those relating to pregnancy and maternity, unworkable, and cut across the protected characteristic of sex in an incoherent way.
A certificated sex interpretation would create two subgroups within those who share the protected characteristic of gender reassignment, giving trans people with a GRC greater rights than those without. It would also create practical challenges for organisations, who would have no way of determining who possesses a GRC, since that information is confidential.
A certified interpretation of sex could give rise to practical problems, such as confusion and impracticability when providing single sex services and spaces. It would also weaken protections given to other protected groups, such as those with the protected characteristic of sexual orientation (for example, by interfering with the ability to have lesbian-only spaces).
The meaning of “sex” and “woman” must be consistent throughout the EA 2010. It is not possible to have different definitions for different sections of the Act.

Protection for trans employees

When delivering the Supreme Court’s decision, Lord Hodge stressed it should not be seen as a “triumph” for one group over another. The judgment emphasises that a biological interpretation of sex will “not have the effect of disadvantaging or removing important protection under the EA 2010 from trans people (whether with or without a GRC)”.

Trans employees will continue to be protected in the workplace on the grounds of gender reassignment. This protects anyone from discrimination or harassment who “is proposing to undergo, is undergoing, or has undergone a process (or part of a process)” to reassign their sex. This applies regardless of whether an individual has undergone medical treatment or surgery.

The Supreme Court also clarified that trans employees will still be able to rely on the protected characteristic of sex under the EA 2010 on the basis of discrimination by association or by perception with their acquired gender. For instance, a trans woman may bring a claim on the ground she is perceived to be a woman, if she can compare her treatment with someone who is not perceived to be a woman. There is no need to rely on a GRC or declare biological sex for such a claim.

EHRC interim update

Whilst the Supreme Court’s decision provides clarity that references to "sex" under the EA 2010 mean biological sex (a "woman" means a biological woman and a "man" means a biological man), practical questions remain about how employers should manage potential issues in the workplace, particularly regarding single-sex facilities, such as toilets and changing rooms.

The Equality and Human Rights Commission (EHRC) has confirmed it will issue a revised Code of Practice and updated guidance in light of the Supreme Court’s judgment by the end of June. This will follow a two week consultation in May to consider the practical implications of the judgment.

To support organisations in the meantime, the EHRC has published an interim update to highlight the main consequences of the judgment. In respect of workplaces, this states:

It is compulsory to provide sufficient single-sex toilets, and where available, changing rooms.
Trans women (biological men) should not be permitted to use women’s facilities and trans men (biological women) should not be permitted to use men's facilities. If they do so, this will mean the facilities will no longer be "single sex" and must be open to users of the opposite sex.
Trans people should not be put in a position where there are no facilities for them to use.
Where possible, mixed-sex facilities should be provided in addition to single-sex facilities.

Looking ahead: considerations for employers

Whilst the Supreme Court’s decision provides clarity that references to "sex" under the EA 2010 mean biological sex (a "woman" means a biological woman and a "man" means a biological man), practical questions remain arising from the decision. These include the implications for people who are intersex (who may not fit neatly into a binary definition of biological sex), and how employers should manage potential issues in the workplace, particularly regarding single-sex facilities, such as toilets and changing rooms.

Since the EHRC’s update is still at an interim stage, and the final guidance may provide more detail, or indeed take a more nuanced approach in light of consultation, it may be advisable for employers to wait for that to be published before taking substantive action. In the meantime, employers may wish to consider:

Policy review: review and, where necessary, amend policies and practices to reflect the Supreme Court’s interpretation of sex under the EA 2010. Consider whether any updated training is required.
Risk assess: evaluate whether any aspects of your workplace are likely to be impacted by this decision. Review associated risks and assess whether any proposed actions are proportionate.
Mixed-sex facilities: the EHRC guidance highlights the importance of providing mixed-sex facilities in addition to single-sex facilities. Review to what extent these are already provided in your workplace. If mixed-sex facilities are not available, consider if any current facilities could be redesignated, or if the provision of mixed-sex facilities could be factored into future building plans.
Data gathering: assess how this decision might affect any data collection and equality monitoring.
Support for employees: the Supreme Court’s judgment has been met with anxiety by many in the trans community. Acknowledge that the decision may have an impact on members of your workplace, particularly trans employees and their allies. Consider whether proactive steps can be taken to support their wellbeing and foster an inclusive work environment.
Ongoing protections: ensure continued protection for trans people in your workplace under the EA 2010. Address any discrimination or harassment concerns promptly under your usual policy.

Many thanks to Eloisa Clegg, current trainee in the team, for her help preparing this blog.

This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.