Members of the House of Lords were invited to declare a marriage valid which had been entered into by a man and a transwoman. They declined to do so. 

Bellinger v Bellinger [2003] UKHL 21, [2003] 2 AC 467

Lord Nicholls said that recognition of Mrs Bellinger as female for the purposes of section 11(c) of the Matrimonial Causes Act 1973: 

“would necessitate giving the expressions ‘male’ and ‘female’ in that Act a novel, extended meaning: that a person may be born with one sex but later become, or become regarded as, a person of the opposite sex” [paragraph36].

He continued:

“This would represent a major change in the law, having far reaching ramifications. It raises issues whose solution calls for extensive enquiry and the widest public consultation and discussion. Questions of social policy and administrative feasibility arise at several points, and their interaction has to be evaluated and balanced. The issues are altogether ill-suited for determination by courts and court procedures. They are pre-eminently a matter for Parliament, the more especially when the Government, in unequivocal terms, has already announced its intention to introduce comprehensive primary legislation on this difficult and sensitive subject.”

The Lords made a declaration of incompatibility under section 4 of the Human Rights Act 1998.