Let me share an incident a friend of mine had. She has custody and bio has some visitation and he gave verbal consent to cruise with their daughter. At the last minute, in Port Canaveral prior to heading to port he called her to say he changed his mind. Threaten to fax custody papers to police and have her arrested. Needless to say she did not cruise that day. She learned not to trust verbal consent from him.
He did this 2 other times gave consent via email but changed mind again and advised her via email. Luckily both other times was done even before final payment.
So off to court she went, judge was not happy with him and new court papers stating she can go whenever and wherever she wants including international and he cannot do anything about it.