Many of which are interpreted under uk law.
That said, I'm not a lawyer, and my experience is limited to trade and finance contracts and compliance statutes. So I'd say I'm more expert than most here on du, but I'm certainly not claiming to be more expert than those who wrote the opinion. I'm just expressing mine.
Thanks for the link. The decision appears to largely rest on the definition of sex from earlier legislation, rather than this act in particular.
Separately, they note that one can indeed officially change one's gender in the uk, and a formal gender reassignment certificate can be obtained to evidence this.
They then argue that treating sex as something other than biological sex would cause "incoherence", for instance in that protections regarding pregnancy were surely intended to apply to trans man, so those biologically female.
My problem with this logic is that first, it ignores the incoherence of having an entire process for gender reassignment, then effectively stating that it doesn't really change anything, and also that clearly, as regarding pregnancy, the key characteristic is something like "those who can get pregnant" and in that context any descriptor such as "woman" is a mere convenience.
They also include reference to practical problems such as that trans women would then be included in lesbian-only spaces and groups, women's sports, etc. some of this is in the clearly bigoted category.
I'm not qualified regarding whether previous laws' definitions should prevail, but I can say having reviewed it, I still think it is in error.