LONDON, United Kingdom (AFP) — Britain’s highest court will hand down a landmark ruling Wednesday on the definition of a “woman,” weighing in on a long-running, divisive debate about biological sex versus gender identity.

The Supreme Court ruling could have widespread implications for sex-based rights across the UK — including access to single-sex spaces for transgender women.

The judges will have the last say in a years-long legal battle between the Scottish government and campaign group “For Women Scotland” (FWS), which believes that only those born female should be legally protected as “women.”

If the court rules in favor of the gender critical campaigners, LGBTQ+ activists fear trans women will no longer be able to access certain facilities like women’s shelters.

At the heart of the debate is the interpretation of the Equality Act 2010, which protects characteristics including sex, gender and gender reassignment against discrimination, and defines a woman as a “female of any age.”

According to the Scottish government, anyone who has transitioned to female and has a Gender Recognition Certificate (GRC), is considered a woman under the Equality Act as well.

However, for FWS campaigners — who believe biological sex at birth is immutable and trumps gender identity — the act does not afford trans women all the protections reserved for those born female.

Supreme Court judges will issue a ruling at around 10 a.m., which will decide whether someone who has transitioned to female and has a GRC is considered and protected as a woman under the Equality Act.