The United Kingdom Supreme Court has ruled that the definition of a woman under the country's equalities law refers to someone born biologically female.
This definition would reject the Scottish government's argument that it should include transgender women. According to Justice Patrick Hodge, five judges at the court ruled unanimously in favour of this decision.
This means that a transgender person with a certificate recognising them as female should not be considered a woman for equality purposes.
The court did emphasise that the ruling "does not remove protection from trans people," who are "protected from discrimination on the ground of gender reassignment."
The case stems from a 2018 law passed by the Scottish Parliament stating that there should be a 50% female representation on the boards of Scottish public bodies.
Transgender women were to be included in meeting the quota.
Feminist groups that had challenged the Scottish government hailed Wednesday's ruling as a victory.
"The court has given us the right answer: the protected characteristic of sex — male and female — refers to reality, not to paperwork," said Maya Forstater of the group Sex Matters.
For Women Scotland, a women's rights group that says they "believe that there are only two sexes," brought the legal challenge.
They argued that the Scottish officials' redefinition of woman went beyond parliament's powers. But Scottish officials then issued new guidance stating that the definition of woman included someone with a gender recognition certificate.
The challenge was rejected by a court in 2022, but the group was granted permission last year to take its case to the Supreme Court.
Aidan O'Neill, a lawyer for FWS, told the Supreme Court judges — three men and two women — that under the Equality Act, "sex" should refer to biological sex and as understood "in ordinary, everyday language".
The Scottish Greens have criticised the ruling, with MSP Maggie Chapman saying it is "deeply concerning for human rights" in a post on X.
Amnesty International said excluding transgender people from sex discrimination protections conflicted with human rights laws.
Amnesty submitted a brief in court saying it was concerned about the deterioration of the rights of trans people in the UK and abroad.
"A blanket policy of barring transwomen from single-sex services is not a proportionate means to achieve a legitimate aim," the human rights group said.
