Datun Yeah, that's a bit of a conundrum, isn't it? And why we went to see our MP on IWD to ask Penny Mordaunt to issue much clearer guidance.
It's a misconception btw that one is not allowed to ask to see a GRC. However, this still doesn't help. What would help is the reasonable belief clause that Church of England etc have, whereby - regardless of birth certificate - a minister (or whatever) of a church that does not permit same-sex marriage can refuse to marry a couple where the minister has the reasonable belief that bride or groom has undergone gender reassignment.
Astonishing that there's such a practical, pragmatic exemption for in my opinion homophobic purposes, but a nearly unworkable one for the purpose of protecting women.
A large number of businesses and organisations are allowed to ask to see a person's birth certificate though. Employers are included in this list.
So in a work setting, it would be very simple to invoke a legal-sex-based exemption - no birth certificate stating female, no access. A biological-sex-based exemption is more difficult unless one is allowed to use the reasonable-belief-rule. However, under the current system, we're talking 3000 males only who are legally female, so I'd say that is workable.
And should female employees then complain about male GRC-holders using their facilities, the employer has the option to invoke a biological-sex-based exemption, no document check needed as the identity of everyone would be well known. That would require some clear work place rules on respecting female boundaries of course.
In an ideal world, employers would provide female-only and male-only facilities with disabled provisions and unisex facilities for all those who do not wish to use the facilities of their own sex.
Anyway, the GRA created a mess by solving this problem in a way that is detrimental to women. As everything about the GRC is confidential and one is not allowed to share information about this, a GRC on its own as proof without falsifying a historic document like a birth certificate would have been far better.
But of course it would not have satisfied the original complaint Christine Goodwin made in that pivotal court case (Goodwin vs United Kingdom, 2002) - that this post-op transsexual was essentially being outed by having to keep the same National Insurance number and via any identity checks.
The court found in favour of Goodwin. Crucially though, the court did so only because post-op transsexuals were such a small, well-defined group. This case was a direct factor in the GRA being established, with the exact same reasoning as to the rarity of transsexuals.