It’s largely a matter of age and size/strength or resourcefulness.
Technically a child never legally has the power to choose with which parent he/she will live (the only person with that power is the judge). But as a matter of life in the real world, when a child knows he/she take Mom or Dad in a fight and/or knows how to sneak off to the other parent’s house, that’s usually when the child has the de facto power to “decide” where he/she is going to live, regardless of what the court orders.
Indeed, courts are reluctant to try to force kids to obey court orders of custody and visitation when they know the kids are big and smart enough to defy the court. Besides, although courts don’t like being disobeyed, they’d prefer kids living with the parent they choose rather than having the kids run away because they are so miserable living with the parent the court ordered them to live with.
Utah Family Law, LC | divorceutah.com | 801-466-9277