UK Supreme Court rules legal definition of a woman is based on biological sex.

On 16 April 2025, the Supreme Court delivered a landmark ruling that the terms “woman” and “sex” in the Equality Act 2010 refer to a biological woman and biological sex.

This decision follows a long-running battle between the Scottish government and a women’s group after the Scottish government argued that transgender people with a gender recognition certificate (GRC) are entitled to sex-based protections, while For Women Scotland argued they only apply to people that are born female.

The decision is said to mark the end of a long-running legal dispute which began in 2018. This started when the Scottish Parliament passed a bill designed to ensure gender balance on public sector boards. For Women Scotland complained that ministers had included transgender people as part of the quotas in that law. Since forming the For Women group, they have consistently argued for women’s only spaces including writing to Scottish councils to ask for single sex toilets in schools and seeking to remove trans women from the definition of women in the Gender Representation on Public Boards (Scotland) Act 2018.

The Supreme Court says its interpretation should not remove protection from transgender people, whether or not they have a Gender Recognition Certificate (GRC). The Supreme Court was careful to point out that transgender people have a number of legal protections from discrimination on the grounds of gender reassignment.

The Supreme Court unanimously ruled that the terms woman and sex in the Equality Act 2010 refer to a biological woman and biological sex.” Lord Hodge, delivering the judgement said the definition of sex in the Equality Act 2010 makes clear that the concept of sex is binary, a person is either a woman or a man” Lord Hodge outlined nine reasons why the judges’ ruled as they did.

The decision could have far-reaching implications across Scotland, England and Wales. Gender reform has been a political battleground, and the decision will almost certainly have implications for political parties on a UK level too. Further implications could include how it affects the running of single-sex spaces and services, and how measures aimed at tackling discrimination will operate in the future. This ruling has already seen mixed reactions. The UK government says the ruling brings clarity and confidence for women and service providers such as hospitals, refuges and sports clubs whereas Scottish Greens says the ruling is deeply concerning for human rights.

Whilst this ruling does not alter existing laws, we can expect to see this continuing legal debate heading back to a political one.

If you have further questions on this matter, please contact one of the Employment Team who would be happy to help!