"CoL's barrister today put the argument (one among many) that since the division is by gender identity, it's not trying to be a separate sex service."
The WI made a similar argument. They said:
"The Defendant is not relying on Schedule 16 EqA to create a single
sex association"
and
"As a membership association, the Defendant is entitled to set a subjective
Membership Criterion if it wishes to do so."
Part of DH's reply to that was around the issue that @BrokenSunflowers mentions above.
There was a sex discrimination case back in 1996 (Smith v Safeway Plc [1996] EWCA Civ J0216-2, [1996] IRLR 456) involving men and women having different uniforms and dress standards at work.
The court held that it was not discrimination to require different uniforms etc because it meant that both sexes had a "conventional" appearance. The judge noted that a code that applied equally to both men and women could still treat one sex less favourably:
“As [counsel for the employers] has pointed out, a code which made identical provisions for men and women but which resulted in one or other having an unconventional appearance, would have an unfavourable impact on that sex being compelled to appear in an unconventional mode. Can there be any doubt that a code which required all employees to have 18-inch hair, earrings and lipstick, would treat men unfavourably by requiring them to adopt an appearance at odds with conventional standards?”
In this example, the treatment complained of is not merely a requirement to wear lipstick, it is a requirement for male employees to dress unconventionally for their sex while female employees are permitted to dress conventionally for their sex.
In the case of the WI, they had a requirement to "live as women". In a similar manner to above, "living as a woman" is not going to be a burden for women as we only need to carry on living as we always have done within the very broad parameters of whatever “live as women” means. Women are not required to alter how they live their lives in any way.
[Please note, I am not in any way equating "wearing lipstick" with "living as women" in any way at all]
In contrast, a requirement that men must “live as women” involves a much greater burden. It involves utterly rejecting a conventional lifestyle, it may also involve the use of drugs and/or surgery.
So, a man is required to live a life outside of any sort of meaningful, conventional understanding of what being a man is. Women just have to go on living as they always have done. Framed like this, a trans-inclusive policy is not neutral as between the sexes and a man is treated less favourably than a woman.
The same would also apply in reverse to a woman who wanted to enter a trans-inclusive men's space.
There's also a complicated argument why this is direct rather than indirect discrimination.
In the CoL case though I think the term they use is anybody who "identifies as a woman". I don't know how much of a difference there is between a requirement to "live" as a woman and a requirement to "identify" as a woman.
.
Another thing to consider, I believe that a pp mentioned about there being a constitution and it mentioning men and women. This is another area to look at.
The CoL may argue that the meaning of the word 'women' has changed since whenever the constitution was written so as to include trans-identifying men.
And, it is true, that the meanings of words or what is included within a concept or category (women in this case), can change over time. The concept of ‘cruel and unusual punishments’ has not changed over the years since the Bill of Rights 1689, but many punishments which were not then thought to fall within that category would now be held to do so.
But what you cannot do is to construe a word to mean something conceptually different from what contemporary evidence shows must have been intended at the time.
To try and include a group (men) that is conceptually different from the ordinary, accepted, meaning of “women” is not possible without expressly altering the constitution to reflect that change (or so my DH argued).