Legal Question in Family Law in Connecticut

A minor who is atleast 16, or his/her parent or guardian, may petition the probate court, or the superior court for juvenile matters, for an order of emancipation. If the minor is or was married, or is a member of the armed forces, or manages his/her own financial affairs and is living separate from his/her parents, or for good cause shown, it's in his/her best interest, the court may grant the request.

Realistically, you can't stop the 17 year old from moving out and, realistically, no one can make him/her return.