Who is a man and who is a woman? Implications of the UK Supreme Court decision

On 16 April 2025, the Supreme Court of the UK ruled that when interpreting the UK's Equality Act (2010)-the Act of the UK Parliament that details protections against unlawful discrimination-the terms 'man', 'woman' and 'sex' pick out 'biological sex' (defined in the Court's ruling as 'the sex of a person at birth') and not also 'certificated sex' (defined in the Court's ruling as 'the sex attained by the acquisition of a Gender Recognition Certificate'). Some have argued that the Court's decision represents a significant setback for trans people, while others have welcomed the perceived clarity the decision has provided. The decision has had, and will continue to have, wide impact, such as on the lawful operation of single-sex spaces and services in the UK. Scrutiny of the Court's judgement is therefore warranted. The judgement was based on an interpretation of what Parliament intended in the Equality Act, but there are unresolved questions: (1) Is the Court's interpretation of what Parliament intended the terms 'man', 'woman' and 'sex' to refer to correct? (2) Was the Court's ruling made in a sufficiently just way? With these questions in mind, this article has two main aims. First, to summarise the Court's recent decision and its social impacts. Second, to stress the importance of procedural justice in evaluating this verdict. This article thereby presents a preliminary case for the adequate consultation of all relevant stakeholders in potentially contentious legal decisions-especially where significant practical consequences for different social groups are likely.