But think two moves into the game. The Federal Government has already passed laws which make selective discrimination illegal.
The Federal Government, under Title VII made it illegal to discriminate on the basis of gender, race, religion.
The Fair Housing Act made it illegal to discriminate on the basis of marital status. It took a long while for FNMA/FHLMC to catch up with the reality of the Fair Housing Act. But they eventually changed their underwriting rules to comply with the Fair Housing Act, so that they conferred upon couples who lived together the same benefits as those who were married.
So, it is inevitable that since there is in place a Federal law, Title VII, which mandates non-discrimination based upon gender, that someone will bring a suit to insure that girls will also be required to register for the Selective Service.
While mine is a logical conclusion, I am not arguing that what is in the law is correct or welcome.