I cannot answer this question for all jurisdictions, but I can tell you how the law applies in the jurisdiction where I practice divorce and family law (Utah).
A divorce or other kind of child custody court has jurisdiction to determine custody and parent-time regarding minor children. A minor is a person under the age of majority.
In Utah, the age of majority (the age at which a person is legally an adult) is 18 years (fun fact: this is also true of every other state in the United States except three; in Alabama and Nebraska the age of majority is 19 years and in Mississippi it’s 21 years).
So in Utah, once a child has reached the age of 18 years, he/she is no longer a minor but an adult, and the divorce court no longer has the power to make or enforce orders regarding “custody” of the “child” because at the age of majority a person is no longer subject to the custody and control of his/her parents, and thus no longer subject to the jurisdiction of the divorce court in those regards either.
Thus, when a child is no longer a child due to turning 18 years of age, nobody can tell that child what to do when it comes to when and how that person chooses to interact with his/her parents. And as long as a parent is not otherwise restricted from communicating or having contact with his/her child (whether the child is a minor or an adult) by a valid court order such as a restraining order or stalking injunction or protective order, then that parent and his/her adult children are free to interact with each other as they please.
This does not mean that doing what one chooses is without consequences of any kind. If you want to spend time with your father against your mother’s wishes, as an adult you’re free to do so, but that obviously won’t protect you from your mother’s disappointment or anger over it.
Utah Family Law, LC | divorceutah.com | 801-466-9277