If the WI want to interpret "women" as including trans women, the courts will allow them to do so provided the result does not breach the law.
Which they inevitably will - they're subject to the Equality Act!
Do you think they will have the discipline to never turn away a man, or write that they are for women only anywhere else, where the enforcers of Equality Act will see it?
The breach will come from them misrepresenting themselves as being single-sex for women - which is to the detriment of women - or, much more starkly, from discrimination against men.
With the ambiguity about the SSEs totally removed, both of those breaches which we've long discussed seem like clearer legal calls.
Oh, and btw, an earlier 'club for trainspotters' analogy doesn't work - I do not believe they exist. There are trainspotting clubs which are open to all. Not clubs that ask you if 'you are or identify as a trainspotter'.
That analogy would only work if the WI could rework itself to say it did womanning but everyone was welcome. As with the trainspotting club, their FAQ would have to have entries like. 'Who can enjoy womanning? - Traditionally, womanning has been thought of as being specifically for women, but anyone can do it, and our society is open to everyone of either sex. We are a fully inclusive organisation, and are not using the single-sex provisions of the Equality Act.'
They're going to have to lay it on thicker than the trainspotting club because the trainspotting club presumably isn't going to be calling itself the Trumpton Men's Trainspotting Club, and needing to asterisk the 'Men's' out of existence...
Meanwhile the current 'Can men join? No.' is almost comical in how much in breach of the EA it is now exposed as.