Protection of employees is weaker than anywhere else in the US. The Northern Mariana Islands have been accused by the US Federal Government and various other organizations for enslaving foreign workers (particularly from China and the Philippines) and immigrants in sweatshops and prostitution.
It can be as low as 18 or as high as 21 depending on where the child lives. In Delaware, the age of majority is 18. However, almost all states allow the child, a parent or a guardian ad litem to write to the judge and/or petition the court for modification of the original custody agreement.
(1) Children can choose to live with the parent who has promised them inappropriate benefits, a new car, or no curfew for example. (2) Children can choose to live with the parent they feel needs them. That puts the child into a parental role which is harmful. It is the parents' job to take care of the children, not vice versa. (3) Children can choose to live with the parent they hardly know because they have a fairytale expectation about how wonderful that parent will be. That fantasy seldom turns into reality. (4) Children can choose to live with the parent who has more money.