UK Supreme Court confirms "woman" in Equality Act 2010 means biological sex

For Women Scotland Ltd (Appellant) v The Scottish Ministers (Respondent)

The recent UK Supreme Court decision in For Women Scotland Ltd v The Scottish Ministers [2025] UKSC 16 has brought legal clarity to the question: who qualifies as a "woman" under the Equality Act 2010?

This legal dispute challenged whether a trans woman who has obtained a Gender Recognition Certificate (GRC) can be recognised as a "woman" by the Equality Act 2010 (EA 2010). The context of this litigation stems from the explicit provisions in section 9(1) of the Gender Recognition Act 2004 (GRA 2004), which states that a person who has acquired a GRC must be recognised as their acquired gender "for all purposes". This formed the basis of the central question in the appeal: whether protections for "women" under the Equality Act can expressly displace the provisions in section 9(1) of the GRA 2004.

The appeal centred on Scottish statutory guidance issued under the Gender Representation on Public Boards (Scotland) Act 2018, which sparked a long-running legal dispute. Aimed at improving the representation of women in the Scottish public sector, the Act defined the term "woman" to include trans women, thereby broadening its scope beyond biological sex.

Initially, this definition was challenged as beyond the legislative scope of the Scottish Parliament in 2020 by a campaign group, For Women Scotland Ltd, the Appellant, on the basis that equal opportunities law is a reserved matter under UK jurisdiction. After a successful challenge, revised guidance was issued asserting that trans women with a GRC were legally "women" and represented "women" under the Gender Representation on Public Boards (Scotland) Act 2018. Ultimately, this guidance granted transgender women protections based on their legally acquired sex under the EA 2010.

The revised guidance was subject to subsequent judicial review, where the Appellant, For Women Scotland, argued that an interpretation based on certificated sex rather than biological sex was unlawful and distorted the concept of being a "woman". The matter was referred to both the Outer House and the Inner House of the Court of Session in Scotland, which upheld the revised guidance. FWS appealed to the UK Supreme Court, which unanimously allowed their appeal.

What is now the legal definition of a woman and sex?

Following the Supreme Court's unanimous decision, the legal definitions of "woman" and "sex" are to be interpreted biologically, not by legal status, for the purposes of the Equality Act. The judgment affirmed that "as a matter of ordinary language, the provisions relating to sex discrimination can only be interpreted as referring to biological sex" (para 168). Therefore, the term "sex" refers to biological sex and the term "woman" refers to a biological female regardless of a Gender Recognition Certificate. This means that a trans woman is not considered a "woman" under the Equality Act, even if she has legally changed her gender under the Gender Recognition Act 2004.

As the Court stated: "The meaning of the terms 'sex', 'man' and 'woman' in the EA 2010 refer to biological sex, as any other interpretation would render the EA 2010 incoherent and impracticable to operate" (para 264). The ruling aims to ensure that sex-based rights and protections remain coherent and enforceable.

One of the key considerations in the reasoning was the need for legal coherence. The Court argued that defining "woman" based on an acquired GRC was divisive and created the potential for inconsistency. This is because possession of a GRC is confidential and applies to a very small proportion of the trans community—only around 8,000 people have applied for a GRC over the past 20 years.

The Court considered eight areas under the EA 2010 where a definition based on biological sex would bring greater legal clarity. These included the following protections:

1. Pregnancy and maternity
2. Freedom of association for lesbians and gay men
3. Freedom of association
4. Positive action
5. Occupational requirements
6. Single-sex spaces
7. Sport
8. Data collection

The Supreme Court therefore unanimously allowed the appeal, clarifying that the terms "sex" and "woman" refer to biological sex, not to the acquired gender recognised by a GRC or a subjective gender identity.

How does this judgment affect future unlawful discrimination claims?

This ruling will affect how discrimination claims are assessed under UK law. The law will now protect biological women and trans women under separate provisions in claims involving sex-based protections.

The decision is likely to prompt a review across public, sporting, and employment sectors to ensure gender policies align with the Equality Act 2010. This includes ensuring that policies meet requirements "for reasons of privacy, decency, to prevent trauma or to ensure health and safety" in line with the Act’s statutory interpretation. By affirming that "sex" means biological sex, the Court has drawn a clear boundary around who may claim protection as a woman under the Equality Act.

Trans women, even those with a GRC, cannot bring claims for sex discrimination as "women". Instead, they must rely on the separate protected characteristic of "gender reassignment", as defined in section 7 of the Equality Act 2010.

Whilst the ruling specifies that the term "woman" refers to biological females, it is important to emphasise that this does not remove protections for transgender individuals. The ruling limits the scope of legal recognition under the definition of "woman", but trans people remain protected against discrimination.

Trans individuals continue to be protected under the Equality Act 2010 through the characteristic of "gender reassignment", which covers discrimination, harassment, and victimisation—whether based on their actual or perceived gender identity.

The ruling aims to provide courts with "clear, consistent, and workable" guidance for those applying the Equality Act 2010. The GRA 2004 does not amend the meaning of "woman". The decision reflects the legal principle that statutory interpretation should follow the ordinary meaning of words unless Parliament explicitly provides otherwise.

In the context of employment and representation, initiatives aimed at improving female representation will now apply exclusively to biological women. The judgment aims to strengthen the legal basis for maintaining women-only spaces and services in a consistent and coherent way. However, the practical impact of this ruling remains to be seen—highlighting the importance of ensuring appropriate protections remain in place for trans women under UK law.