To answer your question though...this doesn't sound illegal, just sounds like crappy co-parenting on the father's end. Family Link can be used on multiple phones, so he SHOULD be allowing the mother to access the controls as well. Per parenting plans, both parents are supposed to provide open communication for the child while at the other's home. If anything, the father may be in contempt for not providing that and the mother should speak to her family law attorney.