What's good for the goose is good for the gander

What's good for the goose is good for the gander.

If it's ok for the girl to do something, it's ok for the guy also. It gives implied permission for both people in a relationship to do something that would not ordinairly be permitted by the other person.

My wife is spending too much money on the credit card, so I guess it's ok for me to also. What's good for the goose is good for the gander.