Tennessee Code Title 40. Criminal Procedure § 40-5-201

(a) The legislative body of any county having a metropolitan form of government may, by ordinance, create the position of one (1) or more judicial commissioners.

(b) The duties of the commissioner or commissioners include, but are not limited to, the following:

(c) The legislative body of any county having a population of not less than twenty-one thousand five hundred (21,500) nor more than twenty-one thousand seven hundred (21,700), according to the 1980 federal census or any subsequent federal census, may, by resolution, create the position of one (1) or more judicial commissioners pursuant to this part.