I'm looking for the problem and can't find one, even when I tilt my head and squint the worst outcome is that there might be issues with single sex spaces + government records nobody cares about.
(I think) it was in this thread that I said that the law had, until last week, been a bit murky. Case law had developed in such a way that the transwomen had the expectation of being able to use womens spaces and services unless that service provider excluded them as a "proportionate means to a legitimate aim" - essentially, they had to be prepared to argue in court why a troon shouldnt be able to use or access their space or service like any other woman.
This isnt what the equality act actually says but it is how it had been interpreted, leaving businesses and HR departments preferring to allow troons to shit with the real women unless they were prepared to make a political statement about keeping them out.
This ruling flips that on its head. They've said for the purposes of the equality act, transwomen are men. That means that if you run a single sex space or service you only have to be prepared to justify why any man should not use it - which frankly isn't hard to do at all. Men aren't taking pub chains to court because they cant piss in the ladies toilet and if they tried it would go nowhere.
And so the supreme court ruling leaves all the troons with all the other fellas tryign to avoid standing next to someone at the urinals. They can still take legal action for discrimination - but because they were being discriminated against because of their gender reassignment, not because they're being treated the same as anyone else of the same sex.
So the default is that troons need to stay out of womens spaces and services unless that service provider makes it clear it's actually a mixed sex service, at which point anyone could use it. New EHRC guidance will be out before long which will make it more clear.
There's an irony in all this in that GRCs have no impact on any of the above. The scottish government insisted that a GRC made no difference to the equality act, so having self id for GRCs would make no meaningful difference. This was cast into double by a ruling in a scottish court who ruled that a GRC does change legal sex under the EA, which is why it ended up at the high court who have actually agreed a GRC doesnt make much difference, but not in the way that troons were hoping.