I think the whole thing is being overthought. Legal or not, unless there is a change then at some point in the future it will attract a lot of negative attention and may well come to a highly publicised challenge. Why not just pass it to the grass roots, the squads, to be allowed to take in males, females and others as their membership sees fit. Surely that would keep the committees's nose clean without having to make any major announcement or get involved
Would it work though, or would it just make a longer trail of people to bury it and/or to sue over it? Devolving the issue down to squad level would just mean that anybody who believed they had grounds to mount a legal challenge would mount it against the individual squad(s)/squad leader(s) who chose to have a male only membership policy, and it wouldn't necessarily absolve the committee entirely, as there would still be the angle that they permitted such discrimination in an event they oversaw if anyone their was mileage in running with it.
Its a step in the right direction though, and for sure its not an issue thats going to go away, so it either needs a plan, or quite rightly as you say, at some future time, maybe soon and maybe not, its going to blow up, possibly spectacularly in folk's faces. 35 years ago any mention of including other genders made by the general public were few and almost all made in jest. Different story now, the number and volume of the critics has been increasing year on year and show no signs of slowing down, and they'd deadly serious.
While the its a "private party" angle and we'll run it as we want to run it argument, is all well and good in many respects, it falls down where the event relies on public areas etc to exist. Were it held wholly on private property little could be done to change things, but it is only as long as the event has the goodwill and tolerance of the general public to give over the various roads, venues etc utilised and "let it happen" that it can continue, and unless those overseeing their "private party" in those areas address the concerns of the rest of the population who tolerate it and let them get on with it, they're living with the apparently steadily increasing risk of people starting to feel strongly enough about things that they decide to withdraw their goodwill and tolerance of the event.
UHA's predecessor was the tar barrel. It had its supporters or it would never had become established in the first place or lasted as long as it did. Presumably any detractors in the early days were few, but times move ahead, things change and attitudes change, and eventually the detractors outnumbered the supporters leading to it being banned. To continue with any sort of similar tradition the tar barrellers had to invent UHA from the bottom up, and could only manage to include tentative tips of the hat to their former activities for it to be acceptable in the age in which they were living.
Credit to them, they must have done a good job, for what they designed has endured relatively unchanged for over a century and has been extensively supported during that period. Times though have again moved on, much has changed and attitudes have dramatically changed in that period, UHA is now of an older vintage than the tar barrel was when it was judged as unacceptable for the times, and folk apparently in ever increaseing numbers are again questioning UHA's acceptability in the times in which we live.
While UHA as it stands may well be believed to be "legal", that has no bearing on its social acceptability. Those running the event can either take the view that the levels of detraction and criticism are exaggerated and that the apparently ever growing opposition to gender based entry has or will shortly peak and subside, or they can address the issue by evolving their event to better suit the times and attitudes.
The tarbarrellers by most accounts were made aware over an extended period that their activities were bcoming less and less tolerable, yet they chose to change their ways little if any, and history records their fate from making that choice. Maybe UHA is big enough and can rely on enough support to continue as is for years if not decades to come, maybe it can't. One thing history is very clear on is that the survivors are those who evolve and adapt as their enviornment changes around them, those who don't ultimately die out. Its always not so much a case of "if", but when that death will occur.ar b