HI,I don't understand why this parent has your chiold and will not retutn her back to you.Even after a court has order him to do so.HE is not the real parent you are.Your 17 year old child is old enough to speak out to say she wants to come home with you.Maybe there is a reason that she wants to be with him and not you.The 17 year old is almost that age that she can live on her own.So if she doesn't want to come home you should let her  be.You can also try to get some legal help not that it is going to help much.YOU can try.Have you tried to talk to your daughter alone and see what she thinks about this issue and what do she think should be done?