UK Supreme Court Rules Legal Definition of ‘Woman’ Refers to Biological Sex

The UK Supreme Court has ruled that the term “woman” under the Equality Act 2010 refers strictly to biological sex and not gender identity, even for individuals who have legally transitioned and hold a Gender Recognition Certificate (GRC).

The unanimous decision, delivered on April 16, 2025, marks a significant legal moment in the ongoing national debate over sex and gender in public policy.

The case stemmed from a challenge brought by the advocacy group For Women Scotland against the Scottish Government’s attempt to include transgender women in the definition of “woman” in the Gender Representation on Public Boards (Scotland) Act 2018. The Scottish legislation was designed to improve gender balance on public boards by reserving certain positions for women, and it allowed trans women with GRCs to be included in that category.

For Women, Scotland argued that this interpretation clashed with the Equality Act, which they contended was based on biological sex distinctions.

In siding with the campaign group, the Supreme Court ruled that the protected characteristics of “sex” in the Equality Act are grounded in biology, not gender identity.

The judgment affirmed that when the law makes reference to women in the context of single-sex provisions—such as female-only services, spaces, or quotas—it is referring to those who are biologically female.

Transgender individuals remain protected under the separate characteristic of “gender reassignment,” but the court clarified that this does not override sex-based rights.

The ruling has drawn both praise and criticism. Supporters of the judgment, including prominent figures in the gender-critical movement, have hailed it as a victory for clarity in law and the protection of women’s rights in single-sex spaces. Critics, including LGBTQ+ advocacy groups like Stonewall, have warned that the decision could deepen the marginalization of trans people and restrict their access to important services.

This ruling is expected to have wide reaching implications for equality policy across the UK, with public bodies such as the NHS, police forces, and educational institutions likely to re-examine their diversity and inclusion frameworks to ensure compliance. It also sets a legal precedent that could influence future legislation related to gender identity and rights.

As the debate continues over how best to balance sex-based rights and gender identity protections, the court’s decision underscores the complexities involved in defining legal categories in an evolving social and political landscape.