Wyllow3
There are a number of organisations like the WI that have welcomed transwomen, whether they feel the need to clarify or alter is up to them?
There is a long-running controversy about that. I'm not a member, but my understanding is that there has been a backlash against their policy of allowing TW, as it contradicts their purpose of campaigning for issues relevant to women. Someone with more knowledge than I have may contradict this, but I think the controversy started when a TW joined and was welcomed, but rose through the ranks in very short order and is now in a position to influence policy on EDI. There may be more to it than that, but some members are very unhappy, and I believe there were mass resignations.
I don't think there can be legal compulsion for the WI (or anyone else) to refuse to accept TW, but it looks as though the guidance is saying that it can't advertise itself as being a women's institute, as if it accepts men that is not the case. If that's correct, they will have to decide whether to relaunch under a different name or to remain single-sex.
This is yet another way in which the TRAs have worked against the interests of 'genuine' TW, who have fitted in and contributed to the organisation. It does seem unfair on them.