The Supreme Court has yesterday ruled that under UK equality law, the terms “man,” “woman,” and “sex” refer to biological sex, not gender identity.

This decision has significant consequences for employers, particularly in relation to workplace policies, hiring, and inclusion initiatives.

Background: How did we get here?

The Supreme Court case arose initially from a Scottish law which was intended to improve female representation on public boards.

However, that law and its associated statutory guidance defined “woman” as including people:

(i) with the protected characteristic of gender reassignment,

(ii) living as a woman;

(iii) proposing to undergo / undergoing / who have undergone a gender reassignment process.

In 2020, For Women Scotland Ltd, a feminist organisation that campaigns to strengthen women’s rights in Scotland, challenged the above definition. Following a decision of the Inner House in Scotland as to the lawful basis for the definition, the Scottish Ministers issued new guidance.

The new statutory guidance stated that the definition of a “woman” is the same as that in Section 212 of the Equality Act 2010 (“EA 2010”) being that a “woman” is “a female of any age.” Further, it also stated that a person with a Gender Recognition Certificate (“GRC”) recognising their gender as female is considered a woman for the purposes of the guidance to increase the number of women on public boards.

A GRC is a document that allows trans people to change their gender legally. The Gender Recognition Act 2004 established that an adult can receive a GRC if they:

(i) have gender dysphoria,

(ii) provide medical evidence from two doctors,

(iii) have lived as their acquired gender for two years, and

(iv) intend to continue to do so until death.

For Women Scotland Ltd did not agree with this interpretation of the EA 2010 and argued that the definition of a “woman” refers to biological sex, meaning that a trans woman with a GRC (a biological male with a GRC in the female gender) is not considered a woman under the EA 2010, and consequently the Scottish guidance for women on public boards.

Whereas the Scottish Ministers argued that the definition of a “woman” under the EA 2010 refers to “certificated sex”, meaning that it includes trans women with a GRC.

Following the dismissal of the For Women Scotland Ltd’s case at the end of 2022, it appealed to the Inner House where, again, it was dismissed at the end of 2023. The appeal was then put to the Supreme Court to determine the definition of a “woman”, and today we have that decision.

What has the Supreme Court decided?

The Court ruled unanimously that under the Equality Act 2010, the terms “man,” “woman,” and “sex” refer only to biological sex.

Key reasons for the decision include:

• UK laws on sex discrimination (dating back to the Sex Discrimination Act 1975) have always understood “sex” as biological sex.
• While the Gender Recognition Act 2004 allows people to legally change gender with a GRC, it does not override biological sex in the context of equality law.
• Protections like maternity rights, women-only services, and women’s sports only function coherently if “woman” refers to biological females.
• It would weaken the protections given to those with the protected characteristic of sexual orientation e.g. the ability to have lesbian-only spaces and associations.
• Some provisions require this interpretation in order to function such as single-sex spaces and services (e.g. changing rooms, hostels and medical services), communal accommodation and others.

Importantly, whilst the Court was unanimous in its decision, it stressed that this interpretation does not disadvantage transgender people, with or without a GRC, who still have the same protections against direct and indirect discrimination, and harassment.

Why does this ruling matter for employers?

This ruling provides clarity for employers on how to define sex-based protections, particularly in hiring, workplace policies, and compliance with UK discrimination laws. While transgender individuals remain protected under gender reassignment laws, businesses must ensure they correctly apply sex-based rules without legal misinterpretation.

What should employers do next?

Employers now need to carefully review how this ruling affects their workplace policies, diversity programs, and legal compliance.

1. Recruitment & Equality Measures

• When implementing initiatives that promote women (such as leadership quotas), employers must define “woman” as a biological female, not based on their gender identity.
• Employers cannot treat transgender women (those assigned male at birth but legally recognised as female) as women for sex-based equality protections for the purposes of recruitment or advancement initiatives tied to sex.

2. Workplace Policies & Inclusion

• Employers must review their workplace policies relating to single-sex spaces (e.g., toilets, changing rooms, or women-only areas). These spaces should now follow the biological sex definition.
• Businesses should ensure that workplace training and diversity initiatives accurately reflect the legal definitions of sex under the Equality Act.
• Employers must be aware, and their policies must reflect, that trans employees remain protected from discrimination based on gender reassignment, but do not qualify for sex-based protections under the law.

3. Legal Compliance & Discrimination Risk

• Carefully assess how your organisation applies diversity and inclusion policies to avoid misinterpreting the legal protections in place for each protected characteristic.
• If a transgender person is denied access to a single-sex space or role based on this ruling, it will not constitute sex discrimination under the Equality Act. However, transgender employees still have the right to challenge discriminatory treatment under gender reassignment protections.

Failing to align your policies with this ruling could result in legal challenges, particularly in industries where sex-based distinctions play a crucial role, such as healthcare, education, sport, or leadership representation programmes.

If you would like support in ensuring that your business remains inclusive while complying with current legal requirements, our Employment team is here to help.

Please contact us on 0191 384 2441 or email one of our team members directly:

Jonathan Moreland – jonathan.moreland@swinburnemaddison.co.uk

Sharney Randhawa – sharney.randhawa@swinburnemaddison.co.uk

Phoebe Gogarty – phoebe.gogarty@swinburnemaddison.co.uk

We’re here to provide clear, practical advice tailored to your business.