User blog comment:Jed Revenant man/Female Space Marines, or, "Can of Worms, opening."/@comment-3562230-20120423004457

The Sisters of Battle are the Chamber Militant of the Ecclesiarchy and according to the Decree Passive, the Ecclesiarchy can not have any male soldiers. "No men under arms" is the exact wording. That is why they turned to the Sisters of Battle, to circumvent the law.

Female Space Marines can't exist because the genetics don't work.

Anyway, the Imperium is pretty equal in regards to everything else. Women can serve in the Guard, the Navy, Inquisition, even in combat roles.

You are right though that WH40k is a man's game so I doubt too many people complain about the lack of female space marines.

However, I have read some complaints that the Black Library has a lack of female authors and thus female characters in books are portrayed poorly or are non existent. But hey, if someone wants more female main characters, right the books yourself.