Supreme Court backs “biological” definition of woman for purposes of Equality Act

The Supreme Court has ruled that a person with a full gender recognition certificate which recognises their gender as female, is not a “woman” for the purposes of the Equality Act 2010 (EA 2010), and that the meaning of the word woman in the 2010 Act is “biological”.

In For Women Scotland Ltd v The Scottish Ministers [2025] UKSC 16, the Supreme Court unanimously concluded: “The meaning of the terms “sex”, “man” and “woman” in the EA 2010 is biological and not certificated sex. Any other interpretation would render the EA 2010 incoherent and impracticable to operate. […] For all these reasons, we conclude that the Guidance issued by the Scottish Government is incorrect.”

The appeal arose in response to the definition of the term “woman” in the Gender Representation on Public Boards (Scotland) Act 2018 (“ASP 2018”) and associated statutory guidance.

The appellant challenged the lawfulness of the statutory guidance, which has the effect that a gender recognition certificate (GRC) recognising that a person’s gender is female brings them within the EA 2010 definition of a “woman”.

The ASP 2018 and the original statutory guidance defined “woman” as including people: (i) with the protected characteristic of gender reassignment; (ii) living as a woman; and (iii) proposing to undergo / undergoing / who have undergone a gender reassignment process.

However, in 2020, the appellant, a feminist voluntary organisation that campaigns to strengthen women’s rights in Scotland, challenged this guidance.

The Inner House found that the statutory definition was unlawful as it involved an area of law reserved to the UK Parliament, and therefore “fell outside the legislative competence of the Scottish Parliament”.

Following this, Scottish Ministers issued new statutory guidance, which was under challenge in the present appeal.

The new statutory guidance states that, under the ASP 2018, the definition of a “woman” is the same as that in the EA 2010. Section 212 of the EA 2010 defines “woman” as “a female of any age.”

It also states that a person with a GRC recognising their gender as female is considered a woman for the purposes of the ASP 2018.

In 2022, the appellant challenged the lawfulness of the new statutory guidance.

On 13 December 2022, the Outer House dismissed the appellant’s petition, and on 1 November 2023, the Inner House dismissed the appellant’s appeal.

Following this, For Women Scotland Ltd appealed to the Supreme Court.

Introducing the case, Lord Hodge, Lady Rose and Lady Simler observed: “It is not the role of the court to adjudicate on the arguments in the public domain on the meaning of gender or sex, nor is it to define the meaning of the word “woman” other than when it is used in the provisions of the EA 2010. […] The principal question which the court addresses on this appeal is the meaning of the words which Parliament has used in the EA 2010 in legislating to protect women and members of the trans community against discrimination.

“Our task is to see if those words can bear a coherent and predictable meaning within the EA 2010 consistently with the Gender Recognition Act 2004 (“the GRA 2004”).”

Several organisations applied to the court to intervene in the appeal.

Human rights charity, ‘Sex Matters’, whose object is to promote human rights where they relate to biological sex, submitted to the court that “sex” in the EA 2010 should be construed as referring to biological sex principally because (i) trans women, including trans women with a GRC, are protected by the protected characteristic of gender reassignment, and (ii) the wider interpretation of the term “sex” in the EA 2010 leads to “absurd or irrational” results.

The Equality and Human Rights Commission (EHRC) explained its longstanding view and policy position that the terms “sex”, “man” and “woman” in the EA 2010 include those whose sex is certified in a GRC.

However, it recognised that the wider definition which it favours causes difficulties and impairs the operation of the EA 2010 in four areas:

1. discrimination on the grounds of pregnancy and maternity;
2. the protection against sexual orientation discrimination;
3. single-sex services, and
4. communal accommodation.

Outlining the legal background of the case, the judges noted that protection from sex discrimination was initially recognised in the Sex Discrimination Act 1975 (SDA 1975).

The SDA 1975 made it unlawful for a woman to be treated less favourably than a man because of her sex (direct discrimination) and to apply a requirement or condition which applies equally to both sexes but where the proportion of women who can comply is smaller compared to the proportion of men (indirect discrimination).

The legislation also accommodated for exceptions to the general rule - for example, where people would be undressing together, living on the same premises or using sanitary facilities together - considerations of decency and privacy required separate facilities to be provided for men and women.

The judges observed: “There can be no doubt that Parliament intended that the words “man” and “woman” in the SDA 1975 would refer to biological sex – the trans community of course existed at the time but their recognition and protection did not.”

Turning to the interpretation of the Gender Recognition Act 2004 (GRA 2004), the judges noted that Section 9(1) of the GRA 2004 establishes that trans people with a GRC are to be considered their “acquired” gender (meaning the gender reflected on their GRC) “for all purposes”.

However, section 9(3) allows the rule in section 9(1) to be disapplied by a provision in the GRA 2004 or “any other enactment or any subordinate legislation”.

The judges observed that Section 9(3) does not require that legislation expressly disapplies the rule in section 9(1) or that this disapplication arises by necessary implication.

They said: “Section 9(3) will apply where the terms, context and purpose of the relevant enactment show that it does, because of a clear incompatibility or because its provisions are rendered incoherent or unworkable by the application of the rule in section 9(1).”

On the interpretation of the Equality Act 2010, the Supreme Court judges noted there is no provision in the EA 2010 that “expressly addresses” the effect of section 9(1) of the GRA 2004. Therefore, a careful analysis of the provisions of the EA 2010 must be undertaken to decide whether they indicate that a biological meaning of sex is intended and/or that a certificated sex definition would render the provisions “incoherent or absurd”.

Section 11 of the EA 2010 provides:

“In relation to the protected characteristic of sex—

(a) a reference to a person who has a particular protected characteristic is a reference to a man or to a woman;

(b) a reference to persons who share a protected characteristic is a reference to persons of the same sex."

The judges stated: “The definition of sex in the EA 2010 makes clear that the concept of sex is binary, a person is either a woman or a man. Persons who share that protected characteristic for the purposes of the group-based rights and protections are persons of the same sex and provisions that refer to protection for women necessarily exclude men.

“Although the word “biological” does not appear in this definition, the ordinary meaning of those plain and unambiguous words corresponds with the biological characteristics that make an individual a man or a woman. These are assumed to be self-explanatory and to require no further explanation. Men and women are on the face of the definition only differentiated as a grouping by the biology they share with their group.

“A certificated sex interpretation would cut across the definition of the protected characteristic of sex in an incoherent way.”

The judges observed that a “strong indicator” that the words “sex”, “man” and “woman” in the EA 2010 have their “biological” meaning is provided by sections 13(6), 17 and 18 (which relate to sex, pregnancy and maternity discrimination) and the related provisions.

They noted: “The protection afforded by these provisions is predicated on the fact of pregnancy or the fact of having given birth to a child and the taking of leave in consequence. Since as a matter of biology, only biological women can become pregnant, the protection is necessarily restricted to biological women.”

The judges added that additional provisions that require a biological interpretation of “sex” in order to function coherently include separate spaces and single sex services (including changing rooms, hostels and medical services), communal accommodation and single sex higher education institutions.

Finally, the Supreme Court concluded that a biological sex interpretation “would not have the effect of disadvantaging or removing important protection under the EA 2010 from trans people (whether with or without a GRC)” for the following reasons:

• Trans people are protected from discrimination on the ground of gender reassignment.
• Trans people are able to invoke the provisions on direct discrimination and harassment, and indirect discrimination, on the basis of sex.
• In the light of case law interpreting the relevant provisions, a trans woman can claim sex discrimination because she is perceived to be a woman. A certificated sex reading is not required to give this protection.

Allowing the appeal, Lord Hodge, Lady Rose and Lady Simler said: “For all these reasons, we conclude that the Guidance issued by the Scottish Government is incorrect. A person with a GRC in the female gender does not come within the definition of “woman” for the purposes of sex discrimination in section 11 of the EA 2010. That in turn means that the definition of “woman” in section 2 of the 2018 Act, which Scottish Ministers accept must bear the same meaning as the term “woman” in section 11 and section 212 of the EA 2010, is limited to biological women and does not include trans women with a GRC.

“Because it is so limited, the 2018 Act does not stray beyond the exception permitted in section L2 of Schedule 5 to the Scotland Act into reserved matters. Therefore, construed in the way that we have held it is to be construed, the 2018 Act is within the competence of the Scottish Parliament and can operate to encourage the participation of women in senior positions in public life.”

Lord Reed and Lord Lloyd-Jones agreed.

The Equality and Human Rights Commission has said it will now work "at pace" to incorporate the implications of the judgment in its revised Code of Practice, which is expected to be laid before Parliament before the summer recess.

Lottie Winson