The UK Supreme Court has ruled unanimously that, under equalities law, the word "woman" refers specifically to biological females, in a landmark decision with sweeping implications for how sex-based rights are interpreted across Scotland, England, and Wales.

This historic judgement concludes a prolonged legal battle initiated by campaign group For Women Scotland against the Scottish government. The group challenged the government's stance that individuals with Gender Recognition Certificates (GRCs) should be included within the legal definition of "woman" when it comes to sex-based protections.

Delivering the court’s verdict, Deputy President Lord Hodge clarified that the 2010 Equality Act defines “woman” and “sex” based on biological attributes, not legal gender recognition. “The unanimous decision of this court is that the terms woman and sex in the Equality Act 2010 refer to a biological woman and biological sex,” he stated.

While acknowledging the sensitivities surrounding the case, Lord Hodge stressed that the judgment should not be seen as a win for one social group over another. He underscored that transgender individuals remain protected under the law through the characteristic of gender reassignment, which guards against direct and indirect discrimination, as well as harassment.

The case centred on the proper legal interpretation of sex under the Equality Act 2010, particularly in the context of the 2004 Gender Recognition Act, which allows transgender individuals to change their legal sex. The Scottish government had argued that such certification equates to a change in sex “for all purposes,” a position the court ultimately rejected.

Campaigners from For Women Scotland, who have long argued for a biological interpretation of sex in law, celebrated emotionally outside the court. Susan Smith, co-founder of the group, said: “Today the judges have said what we always believed to be the case, that women are protected by their biological sex. Sex is real and women can now feel safe that services and spaces designated for women are for women and we are enormously grateful to the Supreme Court for this ruling.”

The UK government welcomed the decision, calling it a move that ensures clarity and security for women and institutions. A spokesperson remarked: “Single-sex spaces are protected in law and will always be protected by this government.”

Equalities Minister Kemi Badenoch also hailed the outcome, describing it as “a victory for all of the women who faced personal abuse or lost their jobs for stating the obvious.” However, she reinforced that transgender individuals would continue to be protected from discrimination under the Equality Act.

The decision has drawn sharp criticism from trans rights advocates. Scottish Green MSP Maggie Chapman called it “a deeply concerning ruling for human rights and a huge blow to some of the most marginalised people in our society.” She said it could strip important protections from trans individuals and leave them uncertain about their place in public life.

Vic Valentine, manager of Scottish Trans, expressed dismay, saying the judgment overturns decades of legal understanding regarding the recognition of trans people with GRCs. “This judgement seems to suggest that there will be times where trans people can be excluded from both men’s and women’s spaces and services. It is hard to understand where we would then be expected to go.”

The ruling examined several real-world consequences of recognising "certificated" sex over biological sex. The judges warned such an interpretation would disrupt the definitions of “man” and “woman” in ways that are legally incoherent. It would also, they noted, erode the ability of single-sex spaces to function as intended—citing examples such as medical services, hostels, women’s sports, and changing rooms.

They further argued that including trans women in categories defined by sex could undermine lesbian-only spaces and associations by broadening the definition of who counts as a lesbian in ways that don’t align with biological realities.

The legal battle dates back to 2018, following the Scottish Parliament’s passage of a bill aimed at promoting gender balance on public boards. For Women Scotland opposed the inclusion of trans women in the female quota. The matter went through multiple stages in Scottish courts, with a 2022 decision by Lady Haldane in favour of the Scottish government, interpreting sex as not limited to biological attributes.

Plans by the Scottish Parliament to simplify the process for obtaining a GRC were blocked by the UK government and eventually shelved by Holyrood.

Reacting to the judgement, First Minister John Swinney acknowledged the court’s ruling, saying the government accepted the outcome and would reflect on its implications. “Protecting the rights of all will underpin our actions,” he posted on social media.

Celebrated author JK Rowling, a vocal supporter of sex-based rights, wrote: “It took three extraordinary, tenacious Scottish women with an army behind them to get this case heard by the Supreme Court and, in winning, they've protected the rights of women and girls across the UK.”

Meanwhile, NHS Fife, which is currently involved in an employment tribunal regarding a transgender doctor’s use of women’s facilities, said it would carefully consider the implications of the ruling.