I have to side with mom here. Dad should have thought about this when he was born. She may not have custody but it doesnt mean she doesn't love him and she is still his mother and should be able to voice concerns. Unless a medical problem I agree with waiting now until he is old enough to understand and decide for himself.
There is the issue of circumcision, and there is the issue of a father with sole custody having a legal right to make medical decisions for the child. I'm not debating the circumcision matter.
Doh!
I don't imagine Dad was settling the custody issue while she was in the delivery room.
At birth time, mom's in full control ... regardless of what may happen later.