UK Supreme Court Rules “Woman” and “Sex” in Equality Act Refer to Biological Sex

The United Kingdom’s Supreme Court has delivered one of the most consequential rulings in the country’s recent equality-law debate, unanimously concluding that the terms “woman,” “man” and “sex” in the Equality Act 2010 refer to biological sex.

The landmark judgment, handed down on 16 April 2025 in For Women Scotland Ltd v The Scottish Ministers, resolved a long-running dispute over how sex should be interpreted under the UK’s principal anti-discrimination legislation.

The case centred on whether a transgender woman who possesses a Gender Recognition Certificate (GRC) should be regarded as a “woman” for the purposes of the Equality Act. The Supreme Court unanimously allowed the appeal brought by For Women Scotland and concluded that, for the relevant provisions of the Equality Act, the statutory terms refer to biological sex rather than “certificated sex.”

The judgment has significant implications for how equality legislation is interpreted across Great Britain. It has also prompted renewed debate about single-sex services, public policy, women’s rights and protections for transgender people.

However, the court was careful to stress that its decision does not remove legal protections from transgender people.

Instead, the ruling establishes that two different protected characteristics under the Equality Act—sex and gender reassignment—operate separately.

That distinction is at the heart of the judgment.

A Case That Began With Scottish Public Boards

The dispute originated in Scotland with legislation designed to improve the representation of women on public boards.

The Gender Representation on Public Boards (Scotland) Act 2018 established an objective of increasing the proportion of women appointed to certain public boards. The legislation and accompanying guidance became the subject of legal challenges over the meaning of “woman.”

For Women Scotland, a feminist organisation campaigning on sex-based rights, challenged Scottish Government guidance concerning the definition.

The legal question eventually reached the UK Supreme Court: if a person had a full Gender Recognition Certificate stating that their acquired gender was female, should that person count as a woman for the purposes of the Equality Act and therefore toward the statutory objective for female representation?

The Scottish Government argued that the answer was yes.

For Women Scotland argued that the relevant provisions referred to biological sex and therefore did not include transgender women with a GRC.

The Supreme Court was ultimately asked to resolve the statutory interpretation question.

It did not attempt to settle the broader philosophical or political debate over the meaning of gender.

Indeed, the court explicitly emphasized that its role was narrower: it was interpreting specific provisions of legislation rather than making social policy.

What the Supreme Court Actually Decided

The court's conclusion was unequivocal.

The terms “sex,” “woman” and “man” used in the Equality Act 2010 refer to biological sex.

The justices found that interpreting those terms as referring to “certificated sex”—the sex recognized through a Gender Recognition Certificate—would create significant practical and legal difficulties within the structure of the Equality Act.

The court therefore concluded that the legislation was intended to distinguish between biological sex and gender reassignment as separate concepts.

In the court's words, the provisions relating to sex discrimination could not properly be interpreted as extending the meaning of sex to include certificated sex without making parts of the legislation incoherent or unworkable.

That conclusion means that, for the purposes of the relevant Equality Act provisions, a transgender woman with a GRC is not included within the statutory definition of “woman” when that term is used to identify the protected characteristic of sex.

Importantly, however, that does not mean the person loses protection from discrimination.

The Supreme Court went to considerable lengths to explain this distinction.

Sex and Gender Reassignment Remain Separate Protections

The Equality Act contains several protected characteristics, including sex and gender reassignment.

The court emphasized that these are separate legal protections.

A person who has the protected characteristic of gender reassignment can still bring discrimination claims under the Equality Act.

The Supreme Court also explained that transgender people can, in appropriate circumstances, rely on protections relating to sex discrimination, including situations in which they are treated less favourably because they are perceived to be a particular sex.