The Prison Service breaks the law by detaining trans women in female jails, two barristers have argued in a legal Opinion.
Ben Cooper KC, who specialises in equality law, wrote the Opinion with Myles Grandison, a public law specialist. They argue that women’s prisons must run on a separate-sex basis. In their view, biological sex rather than acquired gender should define that separation.
Their reasoning rests on the position of female prisoners. The authors describe them as a vulnerable minority with their own characteristics and needs. Mixed-sex prisons, they say, cannot meet those needs.
The Centre for Crime and Justice Studies (CCJS) released the document on 22 May. Shortly before, the Government had issued a long-awaited draft code of practice. The Equality and Human Rights Commission (EHRC) drew up the code. It clarifies the legal footing for single-sex services.
That code follows a Supreme Court ruling in April 2025. The court held that “sex” in law means biological sex, not gender identity.
The barristers’ case
Cooper and Grandison say a women’s prison can lawfully operate as a single-sex service only by excluding all men. Admitting some trans women to the women’s estate, they argue, weakens the case for excluding anyone else.
If “some trans-identifying male prisoners are allocated to the women’s estate, it then becomes very difficult to maintain a rational basis or justification for not accommodating other male prisoners (both trans and non-trans)”, they wrote.
The two lawyers describe the current Prison Service policy as unlawful. They also expect it to give rise to claims of sex discrimination.
How the rules have changed
Since 2016, biologically male trans women in prisons in England and Wales could apply to move to a female jail.
In 2019, England’s 12 women’s prisons held 34 trans women without Gender Recognition Certificates in their general population. The rules tightened that year, and again in 2023, making transfers harder to obtain.
By 2022, six of the 168 legally male trans women prisoners in England and Wales lived in women’s prisons.
Richard Garside, Director of the CCJS, acknowledged the strength of feeling. “There has been a lot of anger, toxicity and conflict over the policy of placing some male prisoners who identify as women in women’s prisons,” he said.
He called the issue a sensitive area of public policy. Prison staff, civil servants, politicians and their advisers held a wide range of views on it, he added.
“Whatever individuals’ personal positions may be, however, it is important that the Prison Service, and other organisations operating in and around prisons, do so in compliance with the law as it is,” Mr Garside said.
He hoped people would accept the Opinion as a helpful contribution. Its aim, he said, was to inform decisions that keep the Prison Service lawful.
