Supreme Court Rules “Sex” Means Biological Sex in Landmark Equality Act Case

This ruling from the UK Supreme Court comes after years of legal challenges and debates about how transgender individuals should be included in equality legislation, and how such inclusion interacts with existing sex-based rights.

The case stems from the Gender Representation on Public Boards (Scotland) Act 2018, which aimed to increase female representation on public boards. The Act—and its original guidance—defined “woman” to include not only biological females but also trans women with or without a Gender Recognition Certificate (GRC).

This approach was contested by a feminist advocacy group, which argued that it altered the UK-wide definition of “woman” as used in equality law, which is outside the Scottish Parliament’s devolved powers.

The legal question centred on whether a GRC, granted under the Gender Recognition Act 2004, changes a person’s sex for the purposes of the Equality Act 2010, which protects against discrimination based on sex and gender reassignment, among other characteristics.

The court reviewed the historical development of UK equality law—from the Sex Discrimination Act 1975 through the EA 2010—and found no evidence that Parliament intended to redefine “man” or “woman” as anything other than biological sex.

The court emphasised the practical challenges of interpreting sex as legal or certificated sex. For example:

• Only biological females can become pregnant, making maternity protections unworkable if sex includes trans women.
• Single-sex services (like changing rooms or women’s shelters) would face legal and operational confusion.
• Public sector equality duties would be harder to fulfil if service providers cannot clearly determine which group individuals belong to.

The ruling also warned that a “certificated sex” approach would create two tiers of trans rights—granting more protection to those with a GRC.  The court highlighted that those service providers seeking to perform their obligations under the EA 2010 would have no obvious means of distinguishing between the two trans sub-groups because they could not ask whether if a GRC had been obtained.  That information is private.

Importantly, the court underscored that this interpretation does not remove legal protections from trans people. Trans individuals are protected under the EA 2010 by the protected characteristic of gender reassignment, regardless of GRC status.

This means they remain protected from direct and indirect discrimination, harassment, and can claim sex discrimination if they are treated unfairly based on perception.

The Supreme Court concluded that the EA 2010’s provisions—especially those regarding pregnancy, women-only spaces, sports, and charities—only function properly if sex is interpreted as biological. It ruled that the Scottish guidance incorrectly expanded the definition of “woman” beyond the EA 2010’s scope.

The decision may reshape how public bodies, service providers, and campaigners understand and implement sex-based rights across the UK.

This landmark ruling may spark wider debates on how trans rights are balanced in UK law. While the decision provides clarity on a legal definition, the broader conversation around identity, equality, and inclusivity is far from over.

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