Biological Parents v. Foster Parents

A married couple, both addicted to drugs, are unable to care for their infant daughter. She is taken from them by court order and placed in a foster home. The years pass. She comes to regard her foster parents as her real parents. They love her as they would their own daughter. When the child is 9 years old, the natural parents, rehabilitated from drugs, begin court action to regain custody. The case is decided in their favor. The child is returned to them, against her will. Does ethics support the law in this case? Discuss.