Чаще 50 миль от настоящего местожительства, но, конечно, от штата зависит. Вот, например, о Флориде: "Florida law forbids the permanent relocation of children by more than 50 miles when the parents aren’t married (including divorced parents) unless the other parent agrees in writing or unless a court agrees. If a parent wishes to move children, even if the other parent lives out of state, there is a complicated procedure that must be followed before children can be moved. And the failure to follow this complicated procedure can subject a parent to loss of majority timeshare (“custody”). "