Updated April 16, 2025 at 06:12 AM ET
LONDON — Britain's Supreme Court has ruled that the legal definition of a woman is someone born biologically female.
Wednesday's ruling is the culmination of a long-running legal battle that began in Scotland in 2018. But it has big implications for transgender people across the United Kingdom — at a time when similar legal challenges are underway in the United States, after President Trump banned transgender people from military service.
What does the ruling say?
The court's five judges issued an 88-page judgment. In it, they say the "concept of sex is binary, a person is either a woman or a man."
"The unanimous decision of this court is that the terms 'woman' and 'sex'… refer to a biological woman and biological sex," Judge Patrick Hodge, deputy president of the Supreme Court, told the court Wednesday, summarizing the ruling.
They ruled that a government-issued gender recognition certificate — which can provide legal recognition to a person's new gender — is not enough to qualify that person for all of the sex-based protections that are covered by a 2010 U.K. law called the Equality Act.
How did this case start?
In 2018, a law was passed by parliament in Scotland, which, as one of the United Kingdom's four nations, has its own devolved legislature. That law required half of the board members in all Scottish public organizations to be women. And it included transgender women as part of that, as long as they possess a gender recognition certificate that identifies them as female.
But a group of gender-critical feminists, called For Women Scotland, challenged that law in court. They said it could impact single-sex services for women, including shelters for abuse victims, hospitals and sports. So they sued the state to limit sex-based protections to people born female – and later lost their case in the Scottish courts.
Today, however, the U.K.'s highest judicial body, the Supreme Court, sided unanimously with the For Women Scotland group – and overruled the earlier decision by the Scottish courts.
What's the reaction been?
The ruling is largely seen as a victory for gender-critical groups and a blow to campaigners for transgender rights, who fear it could lead to labor discrimination against people who have been issued these gender recognition certificates.
Inside the courtroom, supporters of For Women Scotland cheered, punched the air, hugged and cried.
"This has been a really, really long road," Susan Smith, co-founder of For Women Scotland, told reporters outside the courthouse. "Sex is real, and women can now feel safe that services and spaces designated for women are for women — and we are enormously grateful to the Supreme Court for this ruling."
But Judge Hodge cautioned people in the courtroom against seeing this ruling "as a triumph of one or more groups in our society at the expense of another."
U.K. law still gives transgender people protection "not only against discrimination through the protected characteristic of gender reassignment, but also against direct discrimination, indirect discrimination and harassment in substance in their acquired gender," Hodge said.
The U.K. government welcomed the ruling, saying it "brings clarity and confidence, for women and service providers" and that "Single-sex spaces are protected in law and will always be protected by this government."
The charity Scottish Trans issued a call to its supporters "not to panic."
"There will be lots of commentary coming out quickly that is likely to deliberately overstate the impact that this decision is going to have on all trans people's lives," the group said in a statement posted on social media.
"Please look out for yourselves and each other today," it adds.
NPR producer Fatima Al-Kassab contributed to this report from London.
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