The Supreme Court unanimously held that the words "sex", "woman", and "man" in the Equality Act 2010 refer to “biological sex”. The court found that these terms cannot be interpreted to include "certified sex" (the legal sex acquired by trans people via a Gender Recognition Certificate) without making the Act incoherent and unworkable in practice. 

Specifically, the definition of "woman" in the EqA 2010 ("a female of any age") is based on biological characteristics. This means that a trans woman who holds a Gender Recognition Certificate (GRC) is not entitled to be treated as a woman under the EqA 2010 for the purposes of the protected characteristic of sex. 

The court reasoned that Parliament intended "man" and "woman" to refer to “biological sex” when the precursor Sex Discrimination Act 1975 was passed, and this meaning was not changed by the addition of gender reassignment as a protected characteristic or by the Gender Recognition Act 2004. The general legal rule is that words should have a clear, consistent, stable, and predictable meaning throughout a statute. The court decided that many provisions within the EqA 2010, such as those relating to pregnancy and maternity, single-sex services, and positive action, only make sense if "sex" is interpreted as “biological sex”. 

The Supreme Court did not define “biological sex”. Many commentators have assumed that “biological sex” and visible “anatomy” at birth are the same, and therefore believe that this judgment creates a rigid binary definition of “sex”. 

An alternative reading of the detailed judgment is possible. The judge’s use of “biological sex” could create an opportunity for a more nuanced, less binary understanding of our current equality laws. “Biological sex” is not defined in legislation, and there is no scientific consensus on the meaning of the phrase. Many respected academic bodies refer to several biological attributes of a person, typically encompassing chromosomes, hormones, anatomy and physiology. There is no rule to say that one aspect of “biological sex” should prevail over the others.  

All we can say for sure (for now) is that a confidential gender recognition certificate (GRC) does not determine “biological sex” and that sex, sexual orientation and gender reassignment were (and remain) protected characteristics under our equality legislation. The legal position, even after this recent judgment, might be more nuanced than some commentators believe. 

Our understanding of a person’s sex has become much more sophisticated since the 1970s, and the everyday meaning of “biological sex” (for many people) is now multi-faceted. The courts have dealt with a complex subject carefully and compassionately, affirming that confidential certificates are not as important as our understanding of our complex sexual identity. 

Trans people continue to be protected under the separate protected characteristic of gender reassignment. This protection applies whether or not an individual holds a GRC.  

Trans people can still claim sex discrimination if they are treated less favourably because they are perceived to be a different sex (their acquired or presenting gender), even if it differs from their biological sex. 

Discrimination can also be claimed if a trans person is treated less favourably because of their association with a particular sex. 

Harassment claims related to sex are also still possible, including where a trans person is harassed based on their perceived sex. 

Trans people are protected against indirect discrimination as a group sharing the protected characteristic of gender reassignment. They may also be able to claim indirect discrimination where they suffer substantially the same disadvantage as members of the sex with whom they identify (via the "same disadvantage" provisions). 

The court noted that the large majority of trans people do not hold a confidential GRC, and their position under the EqA 2010 is not affected by this ruling regarding the definition of sex. However, there will be people with a GRC who may be treated differently under sex discrimination laws, even though they are protected under gender reassignment rules. There will be people who believe that the ruling went too far, and others who will feel that the ruling didn’t go far enough. 

Many commentators believe that this judgment provides some welcome clarity for employers. If there is some certainty, it might only be in relation to an important but specific circumstance, and it might be temporary, if new cases are brought to the courts, and the official guidance is updated. Each business will need to carefully consider its policies and procedures to ensure they align with all aspects of the Equality Act. 

Policies regarding single-sex spaces like changing rooms and toilet facilities should be reviewed. The ruling affirms that providers of separate or single-sex services may lawfully exclude trans people, regardless of GRC status, if one or more of the carefully defined exceptions in the EqA 2010 apply. The prohibition against discrimination based on gender reassignment continues to apply. 

The EHRC's guidance on this is currently under review following the judgment. 

Where there is a genuine occupational requirement for a role to be held by a person of a specific biological sex, employers can lawfully exclude trans people with an acquired gender, even if they hold a GRC. 

Employers implementing positive action measures aimed at increasing representation of a specific biological sex can lawfully exclude trans people holding a GRC from these measures. 

Review policies in these areas, as protection is linked to biological sex. 

For purposes like the Public Sector Equality Duty (PSED) or positive action, collecting data based on biological sex allows for better analysis of distinct discrimination and disadvantage faced by groups based on their shared biology. 

While the ruling is being cited as clarifying the legal definition of sex, businesses must continue to ensure all work colleagues, including trans employees, are treated with dignity and fairness and are protected from discrimination and harassment. It is crucial to be mindful of the potential impact of this decision on trans people and take proactive steps to reiterate commitment to diversity, equity, and inclusion for all. 

The EHRC is reviewing its guidance, including on single-sex services and sports, which is expected to be updated. An updated statutory code of practice on discrimination in goods and services is also anticipated.