In a ruling that could have sweeping implications for trans people in the United Kingdom, that country’s Supreme Court said that transgender women are not legally defined as “women” under equality law.

All five judges on the high court concurred in a Wednesday decision that the terms “woman” and “sex” under the U.K.’s equality legislation “refer to a biological woman and biological sex,” Judge Lord Patrick Hodge said, reading the judgment.

The ruling is a blow to the Scottish government, which was taken to court by an anti-trans women’s group, For Women Scotland (FWS), over a 2018 Scottish law that includes trans women in its mandate for 50% female representation on government agency boards. The group’s challenge was struck down by a court in 2022, but it subsequently appealed the case to the Supreme Court.

All five judges noted that their decision applied only to the language in the U.K.’s 2010 Equality Act and was not a broader judgment on whether trans women are women. The ruling, Hodge said in his remarks Wednesday, is not “a triumph of one or more groups in our society at the expense of another.”

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The high court faced criticism for refusing to allow trans women to participate in hearings, The Guardian reported.

Supporters of FWS — including notorious transphobe “Harry Potter” author J.K. Rowling — hailed the ruling as a victory. Trans rights advocates and the Scottish government lamented the decision; in a statement, Sacha Deshmukh, the chief executive of Amnesty International UK — which argued alongside the Scottish government in court — said there are “potentially concerning consequences for trans people, but it is important to stress that the court has been clear that trans people are protected under the Equality Act against discrimination and harassment.”

The ruling could have wide-ranging effects on how single-sex services, including domestic violence shelters and hospital wards, are run. The case also tracks with efforts in the U.S. to restrict protections and rights for trans people, many of which have stemmed from federal and state governments led by Republicans.