LONDON - The United Kingdom's top court will issue a ruling on Wednesday on the legal definition of a woman under equality laws, a case that could have far-reaching implications for the fractious debate over transgender rights.

The Supreme Court will give its judgment on whether a trans woman with a gender recognition certificate (GRC), a formal document which gives legal recognition of someone's new gender, is protected from discrimination as a woman under Britain's Equality Act.

Campaign group For Women Scotland (FWS) argues those rights should only apply based on a person's biological sex, and is challenging guidance issued by the devolved Scottish government over a 2018 law that was designed to increase the proportion of women on public sector boards.

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Scottish ministers' guidance on that law stated that a trans woman with a full GRC is legally a woman. The Scottish government argues that the British parliament had intended that this should be the case under equality legislation.

Critics argue that, if upheld, such a definition could impact single-sex services for women such as refuges, hospital wards and sports.

Transgender campaigners say if the court rules in favor of FWS, it could lead to discrimination against those with gender recognition certificates, especially over employment issues.

The FWS case was rejected in the Scottish courts, leading to the Supreme Court appeal, with both sides anticipating that Wednesday's ruling could be complicated.

Challenges to Trump orders

The landmark British case is the latest example of the wider debate around transgender rights ending up before the courts.

In the United States, legal challenges are underway after President Donald Trump issued a series of executive orders which include barring transgender people from military service.

FWS lawyer Aidan O'Neill told the Supreme Court in November that the argument that the use of woman and man in the equality act referred to 'certificated sex' was "just wrong", and should be understood in the "ordinary, everyday language" sense.

Lawyers representing the Scottish government, however, said the guidance was lawful and that a trans woman with a full gender recognition certificate is a woman under the law.

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Several human rights organizations intervened in the appeal, with Amnesty International backing the Scottish government and lesbian groups such as LGB Alliance supporting FWS.

In 2022, Scotland's parliament passed reforms to make it easier for transgender people to change their legal gender, including removing the need for a medical diagnosis of gender dysphoria and lowering the minimum age to 16 from 18.

But Britain's Westminster government blocked the law and the Scottish government later dropped a challenge to that decision.