London, United Kingdom (AFP) – The UK Supreme Court on Tuesday began considering a lengthy dispute between campaigners and the Scottish government on the definition of “woman” in law.

The case brought by the “For Women Scotland” campaign group, which believes that sex is biologically immutable, could have widespread implications on highly charged issues surrounding trans rights and how the UK defines gender and sex.

It could also have consequences for the country’s gender-recognition process and access to single-sex spaces for trans people.

The campaigners say the definitions of “woman” in the UK’s 2010 Equality Act and the Gender Recognition Act 2004 are incompatible.

The 2010 Equality Act protects characteristics including sex, gender and gender reassignment against discrimination, and defines a woman as a “female of any age”.

Under the 2004 act, a gender recognition certificate (GRC) allows trans people to legally change their gender to identify as a man or a woman.

The UK’s top court is being asked to consider whether someone who has transitioned to a female is considered and protected as a woman under the Equality Act.

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The landmark case has come to the UK Supreme Court in London after For Women Scotland challenged 2018 Scottish legislation to get more women on public sector bodies.

In guidance issued for the legislation, the devolved Scottish parliament in Edinburgh said someone who has transitioned to a woman and has a GRC would be considered a woman under the Equality Act as well.

For Women Scotland unsuccessfully challenged the guidance, with a Scottish judicial review concluding that sex was “not limited to biological or birth sex”.

The issue of gender transition has become highly polarised and politicised in the UK in recent years and has caused tensions between Edinburgh and London.

Scotland’s devolved government passed a bill in 2022 making it easier for people to officially change their gender.

But in a rare use of its veto powers against the Scottish administration, the UK government blocked that bill.

Britain’s Conservatives, in power at the time, promised to make “clarifications” in the law so that the word “sex” defines biological sex and not gender, and made excluding trans women from single-sex spaces a focal point in their election campaign earlier this year.