A number of discussions have focused on which DSD conditions to consider allowing access to women's spaces. The primary issue of women being allowed to exclude men from spaces gets bogged down in how to draw the line precisely amongst DSDs and the matter isn't straightforward.
Sex differences, as we understand them, are due to two primary factors: the sex chromosome complement and androgen action. The "true intersex" population have atypical forms/combinations of these differences and can be challenging to sort out in the context of the real world where visual impressions have so much weight. This population is much much too small (on the order of 0.01% of the population) for any class effects and none threaten pregnancy. To be sure: conditions like 5ARD (Castor Semenya) are not "true intersex" here, all of the proposed rules below would exclude those males from women's spaces. None of these rules would, of course, tell anyone how to dress, what jobs they can do, how long to keep their hair, who to love etc.
Key "true intersex" cases
There are only a small number of "true intersex" cases to consider that makes the selection of rules difficult:
CAIS - Insensitive to the most apparent effects of androgen action as it is known. Internal testes, no uterus. Cannot produce sperm.
Ovotesticular disorder of sex development - Some have both gonads as mixes of tissue, some specific cases of one ovary and one testis.
XX Male -Most have SRY attached to the X chromosome, a small fraction do not. SRY-ve XX males are believed to be due to the action of genes downstream of SRY that are thought to be (normally) gated by SRY but are not.
Gonadal dysgenesis -Gonads do not differentiate. Female sex differentiation is not dependent on ovarian secretions, so these people will develop more similarly to females in childhood and can have a uterus. Swyer (XY) and Turner (X0) are classic examples. This could even include anorchia (born without testes).
Mosaics and chimerism -Cells are a mix of karyotypes; numerous subtypes and reasons which can display a spectrum of phenotypes.
Exclusion Rules for Women's Spaces
An easy to interpret and apply exclusion rule is needed for most practical purposes. A rule that specified inclusion would almost certainly be difficult to reason about (perhaps that will be clear below).
Talking about sex in many of these individuals is a fraught matter when people do not know and understand molecular details of these conditions, and these people need be able to live in the world with privacy perhaps even legal fiction to make this possible.
Each of the obvious rules below work fine for typical males and females, but partition slightly differently amongst DSDs. "Born with" is presumed in each class.
Potential to make small gametes This is a tricky rule to follow with "potential". Normally we use that mean to cover normal males who may not be producing gametes for any given reason...but all of the key cases do not have the ability to produce small gametes (e.g., CAIS). Do they have such "potential"? Hard to say. You'd have to let in XX males into female spaces with this rule, doesn't make a lot of sense.
Has a testis Seems to make a lot of sense. Admits anorchia into women's spaces, excludes CAIS and some ovotestis.
Has a penis All XX males are excluded from women's spaces as is anorchia. Swyer, CAIS etc. are not excluded from women's spaces here here.
Constituent SRY "Constituent" to cover cases of microchimerism etc. and only SRY (vs. the whole Y chromosome) to capture SRY+ve XX males. SRY -ve XX males would also be in women's spaces though. CAIS would be male, but so would Swyer and some mosaic. This rule admits the very small set of SRY-ve XX males into women's spaces.
It's a lot of thinking to consider such a small population who, again, probably have tiny/no class effect on the class of typical 46,XX females. Any rule could potentially be unfair to some class in a way that we may not know yet.This is just a draft to outline the question. Perhaps there are some thoughts or corrections that can improve the presentation above.