The UK Supreme Court’s Unworkable Sex Definitions in For Women Scotland

On 16 April 2025, the UK Supreme Court decided in the case of For Women Scotland Ltd v. The Scottish Ministers that the term “woman” in the Equality Act 2010 refers to “biological sex” and thus excludes trans women. As many commentators have stated, this presents a major setback in rights protection and equality law doctrine, which pits trans women’s rights against cis women’s rights, presuming an inherent conflict between different groups of women who are all affected by patriarchy.

The appellant challenged a statutory guidance promulgated by the Scottish Ministers which indicated that trans women who are legally considered female by having obtained a full Gender Recognition Certificate (GRC) could benefit from specific positive action measures targeted at women. The specific measures aimed at the appointment of 50% of women to non-executive posts on public boards provided by the Gender Representation on Public Boards (Scotland) Act 2018.

The Gender Recognition Act (GRA) 2004 establishes that a person can change their legal gender by receiving a GRC. It has the effect of changing the person’s legal sex for all purposes (s9(1)), unless this effect is negated by another legal provision (s9(3)). The Equality Act 2010 prohibits discrimination on the basis of sex, but it allows sex-segregation under specific circumstances, such as in the provision of services, communal accommodation and sports.

The central question in the case was thus whether trans women who have obtained a GRC, and are therefore legally of the female sex, can be excluded from the protection afforded to women under the Equality Act 2010. In other words, does the definition of sex in the Equality Act 2010 negate the effects of changing legal sex for “all purposes” under s9(1) of the Gender Recognition Act 2004?

At the first instance and on appeal, the judges rejected the appellant’s challenge and held that the term “woman” under the Equality Act 2010 includes cis women and trans women who have obtained a full GRC. Yet, in a calamitous judgment, the Supreme Court decided differently. The case raises numerous issues regarding (1) the sources of information used by the judges to make their decision, (2) the risks associated with interpreting “sex” as “biological sex”, (3) the lack of understanding intersectionality, (4) the future of the GRA 2004 and (5) the impact on the lives of trans people in the UK.

Disregard for the Voices of Trans People

The judgment fully embraces the trans-exclusionary rhetoric of the appellant. From the very first paragraph, it accepts the alleged opposition between “women” and the “trans community”. It proceeds to indicate that the first group only includes “biological women”, who are protected by the Equality Act 2010 under the category of sex, while trans women are actually “biological men”, who are protected under the characteristic of gender reassignment. It also refers to so-called “sex-based rights”, a term that is not a common legal term in the UK or international jurisprudence and used by trans-exclusionary groups in the UK to speak of above-cited exceptions that allow making distinctions on the basis of “sex” in the Equality Act 2010.

The judgment was given without hearing a single time the voice of those whose rights will be significantly curtailed through it. While multiple organisations and individuals applied to intervene in the case, the Supreme Court accepted only four organisations as interveners, including two NGOs that are uniquely focused on advocating for the exclusion of trans individuals from the legal definitions of sex and sexual orientation, namely, ‘Sex Matters’ and a consortium of three trans-exclusionary LGB organisations. Of these, Sex Matters was granted permission to make oral submissions in addition to written ones.

It also accepted written and oral interventions of the Equality and Human Rights Commission, which was called out by the UN Independent Expert on protection against violence and discrimination based on sexual orientation and gender identity in 2024 for a lack of independence and having “inappropriately offered the Government a formula to seek to exclude trans and gender-diverse persons from legal protections that they currently enjoy under the law of the UK and […] international law”. Lastly, it accepted a written intervention of Amnesty International UK, which was, however, not allowed to provide oral statements and its written submission is only referred to in a brief and expeditive sentence in the judgment, while the Court engages thoroughly with the other interventions. Thus, no representatives of LGBTQ or trans organisations were invited to present their arguments and all voices who could have introduced a trans-inclusive narrative were dismissed.

Biological Sex

Another weakness of the judgment is that it relies on the appellants’ claim that “biological sex” is a self-explanatory term with a clear legal meaning. In searching for the ordinary meaning of “sex” in the Equality Act, the Court opposes “biological sex” defined as the sex assigned at birth and “certified sex” defined as the sex legally recognised through a GRC (e.g. §7). As underlined by Damian Gonzalez-Salzberg, the Supreme Court fails to recognise that its definition of biological sex is actually another version of “certified sex” as it is based on “sex certified at birth, rather than later in life”. The judgment does not make any reference to variations in sex characteristics, ignoring the question of how “biological sex” is defined, such as by means of chromosomes, hormones, gonads, appearance of genitalia at the time of birth or any other factor.

Further striking is the Court’s claim that the only difference between men and women is their biology (e.g. §171), which effectively ignores that laws, institutions and social norms have always treated women and men differently, resulting in their different social positions and power. By embracing the idea that only biology makes women and men different, it has undone decades of feminist work opposing the view that gender differences can be attributed to nature. Along the same line, the Court claims that it is women’s “shared biology”, rather than patriarchal norms, which leads them to face discrimination (§171-172).

The Court’s definition of “biological sex” is further revealed as deeply flawed and unworkable when the Court discusses lesbian sexual orientation. The Court clumsily relies on its biological definition of sex to argue that “a person with same sex orientation as a lesbian must be a female who is sexually oriented towards (or attracted to) females (§206).” By arguing that it would result in “inevitable loss of autonomy and dignity for lesbians (§207)” if trans women could be considered as such. The Court’s argument not only denies the lived experiences of many lesbians whose attraction is not determined by another person’s sex as observed on their original birth certificate but also manifestly ignores the fact that cis lesbians’ and bisexual women’s views of trans people are overwhelmingly positive, as recent surveys by YouGov and Just Like Us suggest. The refusal to hear interventions from trans-inclusive lesbians in the case has undeniably contributed to the Court’s narrow and artificial definition of lesbians.

Intersectionality

Despite decades of efforts by black and intersectional feminists (e.g. Crenshaw, Koyama), the judgment demonstrates the Supreme Court’s blatant lack of understanding intersectionality. The Court’s reasoning rests on the idea that, if trans women can claim discrimination under the protected characteristic of “gender reassignment” under the Equality Act 2010, they cannot – or don’t need to – be protected under the characteristic of “sex”. The court thus fails to appreciate that a person could fall under two different grounds of discrimination as they experience multiple and intersecting forms of discrimination, such as trans women experiencing both transphobia and misogyny (“transmisogyny”). Instead, the judges decided that including trans women with a GRC in the definition of “woman” in the Equality Act 2010 would have the unacceptable effect to give them “additional rights” compared to other persons who are protected by the characteristic of gender reassignment but cannot claim sex discrimination, such as trans women without a GRC (§203).

What Is the Value of GRC after the Judgment?

Following the judgment, it is unclear whether obtaining a GRC is still useful. Indeed, it is clear that the change of legal sex permitted by the GRA 2004 does not have effect “for all purposes” anymore. The government’s initial response indicates that the judgment will be interpreted in a way that permits service providers to disregard the legally recognised gender identity of a person who has obtained a GRC, and instead consider only their sex assigned at birth. The effect of the Supreme Court judgment could be seen as going as far as stripping the UK from legal gender recognition – raising concerns about its obligations under international law. Indeed, under the jurisprudence of the ECtHR, legal gender recognition has to be effective and accessible as well as quick and transparent (Hämäläinen v Finland; A.D v Georgia); the judgment casts some serious doubts on the “effective” character of a GRC.

As repeatedly stated in the judgment, the confidential nature of a GRC means that it is impossible to know for service providers if a trans person has obtained a GRC or not. It also means that it is impossible to know if a person is cis or trans. In an odd turn of events, the Court eventually addresses this issue and stresses that trans women can in fact be protected under the ground of sex when they are perceived and thus treated as “biological women” (§250-251). In other words, it is not the legal recognition of sex that matters for being covered by sex discrimination but the perception of others – and thus the person’s passing as a cis woman.

However, whilst recognising this point in relation to sex discrimination, the Court fails to realise that the same principle de facto applies to single-sex spaces since one rarely needs to show the original birth certificate when entering a bathroom or changing room. Instead, one can mostly enter and move in single-sex spaces without problems and scrutiny if one is perceived as cisgender. The Court’s decision, however, will result in increased public policing affecting everyone who does not conform to hegemonic gender norms, including trans persons who don’t pass as well as masculine-presenting cis women. Given that original birth certificates are rarely carried around and that obtaining a GRC is private information, what will they need to do to prove their “biological sex”?

And Now, What?

In practice, it is infeasible for service providers, employers and organisations to force a person to prove that they are cis or trans – despite the argument of the Court according to which defining sex as biological is the only way to provide clarity for them (§203). The decision of the Supreme Court will result in increased gender policing and harassment against gender non-conforming persons (including cis women). Trans persons will continue to live their life but will be under increased scrutiny and pressure to pass and to abandon activities of public visibility and advocacy which could “out” them. In the meantime, trans-inclusive organisations will be under pressure to exclude them from single-sex spaces (as aptly highlighted by Alex Sharpe). This judgment is no less than one more step toward the erasure of trans persons from public life.