My Stepmother Is Planning To Send My Half Sister (06) To Vietnam For 3 Months Without My Father’s Consent.

My ex-stepmother is threatening my father because he does not agree with the situation. My stepmother’s mom (who is not a legal citizen) is taking my half sister to Vietnam for 3 months. So my ex-stepmother isn’t even going. My father is not familiar with the law, and so my ex-stepmother is feeding him lies and also threatening his ties to her if he does not allow it. I do not think it is legal, but I also don’t get any specific laws or information about whether or not it is okay for her to do this at all or without his consent. My father is a Louisiana resident and my ex-stepmother and sister resides in Georgia for additional info. Also, they both are legally responsible for her. If there are any laws against it, does this count as kidnapping if it’s a trip? please let me know.