Physical standards. But there are standards related to form and function, which acquire a moral character, don't you think?
There are plenty of men. Women are not only not physically fit for combat but not spiritually fit according to their form and function. No only this but, no matter how large and chunky a woman is, her connective tissue at articulable joints are not as heavy duty as that of men.
The strength may perform for a time, but damage would accumulate. Would it be moral to have a policy that misuses an organism against its form and function when there are an order of magnitude more organisms whose form and functions are designed for it?
A valid argument against women in combat. But then my argument was agianst men being denied equal protection under that law not pro-women in combat.