The U.K. Supreme Court ruled Wednesday that a woman is someone born biologically female, excluding transgender people from the legal definition in a long-running dispute between a feminist group and the Scottish government.

Several women’s groups that supported the appeal celebrated outside court and hailed it as a major victory in their effort to protect spaces designated for women.

“Everyone knows what sex is and you can’t change it,” said Susan Smith, co-director of For Women Scotland, which brought the case. “It’s common sense, basic common sense and the fact that we have been down a rabbit hole where people have tried to deny science and to deny reality and hopefully this will now see us back to reality.”

Five judges ruled unanimously that the U.K. Equality Act means trans women can be excluded from some groups and single-sex spaces, such as changing rooms, homeless shelters, swimming areas and medical or counseling services provided only to women.

The ruling means that a transgender person with a certificate that recognizes them as female should not be considered a woman for equality purposes.

The ruling brings some clarity in the U.K. to a contentious issue that has polarized politics in some other countries, particularly the U.S. Republican-controlled states over the last four years have been banning gender-affirming care for minors, barring transgender women and girls from sports competitions that align with their gender and restricting which public bathrooms transgender people can use.

Since returning to office in January, President Donald Trump has signed orders to define the sexes as only male and female and has tried to kick transgender service members out of the military, block federal spending on gender-affirming car e for those under 19 and block their sports participation nationally. His efforts are being challenged in court.

Justice Patrick Hodge said the British ruling “does not remove protection from trans people,” who are still protected from discrimination under U.K. law.

The case stems from a 2018 law passed by the Scottish Parliament saying 50% of the membership of the boards of Scottish public bodies should be women. Transgender women with gender recognition certificates were to be included in meeting the quota.

“Interpreting ‘sex’ as certificated sex would cut across the definitions of ‘man’ and ‘woman’ ... and, thus, the protected characteristic of sex in an incoherent way,” Hodge said. “It would create heterogeneous groupings.”

The campaign group Scottish Trans said it was “shocked and disappointed” by the ruling, saying it would undermine legal protections for transgender people enshrined in the 2004 Gender Recognition Act.

Maggie Chapman, a Green Party lawmaker in the Scottish Parliament, said the ruling was “deeply concerning” for human rights and “a huge blow to some of the most marginalized people in our society.”

“Trans people have been cynically targeted and demonized by politicians and large parts of the media for far too long,” she said. “This has contributed to attacks on longstanding rights and attempts to erase their existence altogether.”

Groups that had challenged the Scottish government uncorked a bottle of champagne outside the court and sang, “women’s rights are human rights.”

“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. In 2022, an employment tribunal ruled that she had been the victim of discrimination when she lost out on a job after posting gender-critical views online.