Tenn. Code Ann. § 5-1-114: Interlocal cooperation between contiguous counties

(a) The county legislative bodies of any two (2) or more contiguous counties are empowered to enter into such agreements, contractual arrangements or compacts as they may deem necessary and desirable, in order to provide for the joint conducting or financing of any of the functions or services rendered by or through the county government.

(b) Any county legislative body is empowered to enter into such agreements, contractual arrangements or compacts, as may be deemed necessary or desirable for the county to have any one (1) or more of its services or functions performed by and through the offices and officials of another county legislative body, and any county legislative body is authorized to enter into such agreements, contractual arrangements or compacts as may be deemed desirable or necessary to permit the offices and officials of such county legislative body to perform those services or functions for another county or counties.

(c) Such services or functions shall be performed and provided for in accordance with the terms and conditions as agreed upon between the respective county legislative bodies.