What term describes when a mother gains full custody of a child and the father takes the child unlawfully?

The term that accurately describes a situation where a mother gains full custody of a child and the father unlawfully takes the child is child abduction. This term specifically refers to the act of taking a child away unlawfully from their legal guardian or custodial parent. In this context, since the father does not have the legal right to take the child after the mother has been granted full custody, his actions constitute abduction.

While "parental kidnapping" might also seem fitting, it is often used more broadly, encompassing a range of scenarios involving a parent taking their child without legal right. In contrast, child abduction is a clearer and more specific term focused on the unlawful nature of the act. "Child custody" and "child support" are not relevant to the act of unlawfully taking a child, as they relate to the legal arrangements for custody and financial support for raising a child, respectively.