A guide to the UK Supreme Court ruling on the legal definition of 'sex' and 'woman'

Overview

For Women Scotland Ltd (Appellant) v The Scottish Ministers (Respondent)

Lord Reed, Lord Hodge, Lord Lloyd-Jones, Lady Rose, Lady Simler

On Wednesday, 16th April 2025, the UK Supreme Court issued its ruling following a long-running legal challenge regarding the definition of the term ‘woman’ in law, specifically when understanding the meaning and scope of the term ‘sex’ in the UK’s Equality Act 2010.

This is a landmark ruling, following years of misunderstanding and individual interpretation of the provisions within the Equality Act 2010, which had until this point not been clear in its definition of the meaning of the term ‘sex’, specifically in outlining who these provisions do and do not apply to. 

What is this ruling about?

In its simplest terms, this ruling is in response to attempts to seek clarity on the legal meaning and definition of the term ‘sex’, specifically in its application and interpretation in UK equality legislation.

The case was brought to the Supreme Court by a gender-critical advocacy organisation called ‘For Women Scotland’, following a failed bid for a judicial review of statutory guidance issued by the Scottish Government in 2022. The statutory guidance issued by Scottish parliament outlined that transgender women and men who had attained a Gender Recognition Certificate were legally entitled to be considered as women (for trans women) or men (for trans men) under the sex-based provisions and protections of the UKs Equality Act 2010.

For Women Scotland argued that the Equality Act's definition of ‘sex’ referred only to biological sex and should not include transgender women or men. This argument was, in part, based on a gender-critical ideology that sex is binary, immutable and absolute, and can only be defined by two sexes – male or female. In this ideology, a woman or man is defined only by their sex assigned at birth and a person’s sex cannot be changed, irrespective of the attainment of a Gender Recognition Certificate or any level of medical, healthcare or other interventions.

The Supreme Court found in a unanimous decision that, when referring to the Equality Act 2010, the terms "man", "woman", and "sex" were "always meant" to refer to “biological sex”, and not to gender or gender identity.

How was 'sex' defined prior to the ruling?

The Gender Recognition Act 2004, which predates the UKs Equality Act, is a piece of legislation that allows adults who have gender dysphoria to change their legal sex. It came into effect on 4 April 2005.

The provisions of the Gender Recognition Act allow (amongst other things) transgender people to apply for a Gender Recognition Certificate (GRC) – a document that grants the individual the legal recognition of their acquired sex. As an example, an individual transitioning from male to female, who applies for and is granted a GRC, would be “legally” recognised as female, subsequently allowing them to apply to have the sex marker on identification documents, such as a UK Passport, birth certificate or driving licence changed to reflect their acquired sex.

As a result of these provisions, the protected characteristic of ‘sex’ within the Equality Act 2010 had been widely interpreted to mean that sex-based protections would include trans women (and trans men) who had received certification of their acquired sex, although it was never explicitly outlined with the provisions of the 2010 Act.

The UK Supreme Court ruling made clear that this is not the case, and that acquiring a GRC does not alter a person’s sex for the purposes of the Equality Act, and that while the Gender Recognition Act 2004 allows individuals to change their legal gender, this change does not affect the interpretation of sex in the Equality Act 2010. This ensures that there is a clear distinction between gender reassignment and biological sex in anti-discrimination law.

The ruling

As part of the lengthy 88-page ruling, the Court ruled that the term “woman”, when referring to the protected characteristic of ‘sex’ in the Equality Act 2010, exclusively refers to biological sex, issuing clear guidance following many years of confusion and interpretation. In issuing its ruling, the Court aimed to clarify this definition explicitly when understanding who receives protection under the protected characteristic of ‘sex’, as well as clarity around protections in place for women (explicitly within the judgement, but notably most likely extended to men by default).

This ruling comes at a time where transgender and gender-diverse people are subject to an increasing level of prejudice, hate and intolerance. However, the ruling was intended as a way of settling a long-standing and particularly complicated set of contradictions and confusion within UK legislation, and Lord Hodge, when delivering the ruling, made it clear that:

The ruling does not affect the Equality Act 2010's protections from discrimination by the protected characteristic of gender reassignment. Lord Hodge went on to explicitly acknowledge that transgender people were a vulnerable population that "struggle against discrimination and prejudice as they seek to live their lives with dignity". He further warned that the judgement should not be seen as "a triumph of one or more groups in our society at the expense of another”.

What does this mean?

What we can immediately interpret this ruling to mean practically is that:

• Transgender women (and men) with Gender Recognition Certificates (GRCs) are no longer recognised legally as women (or men) under the sex-based provisions and protections of the Equality Act 2010.
• Any initiatives (including positive action activities) designed to increase representation of women, including achieving targets for including women on boards or in management positions, should consider women only on the basis of their biological sex. It should be made clear that this is not an explicit ruling by the Supreme Court. However, with this new definition of ‘woman’ enshrined in law, anyone claiming discriminatory practice, based on sex, against an organisation that is including trans women within its target demographics [for this type of positive action activity] have an increased chance of their claim being upheld.  
• Access to ‘women-only spaces’ will likely be limited and transgender women explicitly excluded from access to these environments when those exclusions have a legitimate aim. However, it should be noted that this can still only happen where there is a ‘proportionate means of achieving a legitimate aim’. The EHRC (Equality and Human Rights Commission) currently outlines those ‘exceptions’ that allow organisations to “lawfully exclude, modify or limit” access to certain groups “for reasons of privacy, decency, to prevent trauma or to ensure health and safety”.
• Organisations should consider how they currently collect the demographic data of their employees, particularly in documenting the sex and/or gender of their employees. If employers are currently collecting this data only using a single category of ‘sex’ without any explicit references to ‘gender’ or other categories that record self-defined gender, they may want to consider reviewing this in light of the next ruling. 

FAIRER Consulting can support you with this activity or provide guidance if you have any concerns or questions.

Immediate impact

Like most judgements of this nature, the immediate impact and a clear understanding of the implications of this ruling will take time to understand, particularly in its impact on ensuring an inclusive workplace environment for all, irrespective of their sex or gender identity.  

However, within the first 48 hours of the Supreme Court’s ruling, there were some notable statements made that would have an immediate impact, including:

• British Transport Police issuing interim guidance to their police officers that transgender women in their custody would be strip searched by male officers.  
• Baroness Kishwer Falkner of the Equality and Human Rights Commission (EHRC) stating in an interview with BBC Radio 4’s Today programme,  that transgender women were no longer permitted to use women's bathrooms, changing rooms, or play women's sports. Baroness Falkner went on to say:

“…there’s no law that forces organisations, service providers, to provide a single-sex space, and there is no law against them providing a third space, an additional space, such as unisex toilets for example, or changing rooms.” She also said that trans rights organisations “should be using their powers of advocacy to ask for those third spaces”.

Employers’ legal and ethical responsibilities

As a reminder, this ruling relates to the definition of ‘sex’ and ‘women’ in legislation and is not a direction that organisations are now lawfully entitled to discriminate, harass or victimise transgender people. Protections for transgender women (and men) still exist within the Equality Act 2010 under the protected characteristic of ‘gender reassignment’ and therefore organisations are still able (and we would encourage them) to:

• Consider and include transgender women and men in your attraction, recruitment and retention activities
• Ensure that transgender women and men are afforded dignity at work and the right to privacy, should they choose not to disclose their transgender status. There is no legal requirement for transgender people to disclose this information and the provisions within the Gender Recognition Act 2004 still apply, particularly in its direction that employers have a responsibility to maintain the confidentiality of this information whenever it is disclosed
• Continue to include transgender and gender-diverse people when designing and implementing wellbeing and rewards programmes and other EVP-related activities or provisions. The sudden exclusion by omission of transgender people in these provisions or practices could be seen as an example of unlawful (discriminatory) practice
• Provide a suitable working environment, free from discrimination, harassment and victimisation
• Educate your workforce on inclusive practices and raise awareness of the value and importance of difference
• Foster respectful curiosity within your workplaces, encouraging colleagues to increase their own awareness and understanding of transgender and gender-diverse communities and their experiences
  

Organisations are reminded that harassment, as defined in the Equality Act 2010 is:

“…unwanted behaviour [related to a protected characteristic] which has the purpose or effect of violating someone’s dignity or which creates a hostile, degrading, humiliating or offensive environment.”

Unwanted behaviour could include:

• Spoken or written abuse
• Offensive emails
• Tweets or comments on websites and social media
• Images and graffiti
• Physical gestures
• Facial expressions
• ‘Banter’ that is offensive to you

We would suggest that any workplace environment that either encourages or allows transgender employees to be subject to deadnaming, misgendering, intolerance, prejudice or exclusion, as a result of an individual’s known or perceived transgender status, might constitute creating an environment that violates transgender employees’ dignity or creates a hostile, degrading, humiliating or offensive environment.  

Building an inclusive workplace

• Be aware that transgender people might be employed by your organisation, whether you are aware of them or not. Get to know your colleagues and be open to sharing personal information about yourself. Create an environment of conscious inclusion so that your colleagues feel that they are better understood, and they will be happier and more productive.
• Take the time to learn about trans issues – increase your understanding and awareness of the issues unique to trans people. If you are unsure about something, be respectfully inquisitive and ask your trans colleagues about the issues that they face in the workplace. Ask them for their own suggestions to improve the working environment for everyone.
• If you are a manager or senior leader, show that you are open to better understanding the needs of your trans colleagues, and help to create an inclusive culture.
• Help the organisation to review your workplace policies and ensure these policies explicitly mention how you as an employer support trans people within your organisation. You could also develop trans-specific policies – for example, a policy on transitioning at work, with guidance for employees who are transitioning, line managers and human resources. Your workplace policies should establish a strong sense of inclusion and anti-discrimination so that all employees know what diversity and inclusion looks like in the business and what is not tolerated in the workplace.

What employees can do

• Be an ally all year around, 365 days a year, not just during Pride or LGBTQ+ History Month.
• Accept that you will make mistakes and get things wrong. That’s OK! The language that we use, particularly in how we define ourselves, changes constantly. As long as you’re being respectful and treating your trans colleagues with dignity, getting things wrong won’t be as big of a problem as you think it might. Apologise and learn from your mistake.
• If you see something going wrong, or someone being treated badly because they are transgender, step in and do something about it. Offering your help and support to someone who is struggling is a great way of showing that you care and understand the impact on them of inappropriate behaviour.
• Don’t do it for the reward. Being an ally should be something you want to do, because it is the right thing to do. Don’t be an ally because it will help you get that promotion you’ve been chasing, or that pay rise or bonus in next year’s performance review. 

Employee resource groups (ERGs) and staff networks

If you don’t already, this would be a good opportunity to develop and launch a trans-inclusive LGBTQ+ employee resource group (ERG, or staff network). ERGs are a great way of helping advise organisations identify what works well in the workplace, and areas for improvement.

You should also encourage colleagues who don’t identify themselves as LGBTQ+ to support the LGBTQ+ network. These colleagues can work with the LGBTQ+ network to champion diversity in the workplace and the LGBTQ+ network can help implement diversity initiatives and build awareness – e.g., through talks and events.

ERGs are also a great way to help to promote your organisation as being trans-inclusive, ensuring that any information you produce considers and is inclusive of the needs of transgender or gender-diverse people. Making sure that you use any opportunity to talk about, and show, the diversity of your colleagues goes a long way to showing how inclusive you are.

It’s also important for organisations to make clear whether any existing ERGs that exist to support women in the workplace are trans-inclusive or explicitly exclude transgender women. 

Let us help you

FAIRER Consulting recommends that organisations continue to create and foster an inclusive environment, with dignity, respect and cohesion at their heart. If you need any further guidance on how to do so in light of the UK Supreme Court’s ruling, please contact us at info@fairerconsulting.com.