Over the last century, UK law has moved from endorsing, and in some cases mandating, unjust sex discrimination to a robust framework of distinct protections for women and girls. At the same time, our law has extended anti-discrimination protections to people who undergo gender reassignment, culminating in a system where individuals can change their legally recognised sex for some purposes. Sometimes the interests of these two groups conflict, most notably where the law must differentiate based on biological sex in contexts where those with transgender identities wish to be classed by reference to gender identity instead. For a time, there was uncertainty over the precise interaction between these competing interests within equality law. In 2025 this was resolved in a landmark case brought by the feminist organisation For Women Scotland. This book traces the history of how sex changed within our law and what that means for ongoing controversies over single-sex spaces, freedom of belief, freedom of expression, privacy, sport, and sexual intimacy.
