Tennessee Code Title 5. Counties § 5-7-105

(a) The courthouse and all county buildings provided by the county for the county officers shall be erected within the limits of the county town; provided, that the jail and county highway department garage may be erected outside the limits of the county town but within the boundaries of the county; and provided further, that if two (2) or more counties enter into an interlocal agreement providing for a jail or workhouse to serve the counties that are parties to the agreement, then a county that is a party to such an agreement shall not be required to have a jail or workhouse located within the boundaries of the county, but any jail or workhouse serving more than one (1) county shall be located within the boundaries of one (1) of the counties that is a party to the agreement.

(b) Nothing in this section shall be construed as preventing or prohibiting a county that has constructed a criminal justice building or facility, or that uses a building or facility, that is not located within the limits of the county seat, from holding criminal court in that building or facility; provided, that it is located within the limits of the county. If the building or facility is used to hold criminal court, a defendant may be indicted, prosecuted, tried and convicted in that building or facility as if done at the courthouse.