Assuming there was a warrant issued from Campbell County and served on the defendant in Kenton County, he will be held there until Campbell County comes and gets him.
He should be brought before a Kenton County judge and advised he is being held on an out of county warrant.
Hire an attorney in Kenton County to review the matter. Contact Campbell County, speak with the clerk, get the details and arrange to post a bond set there if possible. Your attorney will know what to do to get the case moving. Usually the jailor will contact whoever issued the warrant and ask if they are coming to get the defendant who is being held on their warrant.
I am trying to give you a general answer to your question. We do not have an attorney-client relationship by this response on the avvo website. I have not been retained to represent you. I am licensed to practice law in Kentucky and in federal court in this state and the Southern District of Indiana. You need to seek legal advice from an attorney licensed to practice in your area..