Tenn. Code § 58-8-112
Governmental entities that are parties to existing mutual aid agreements may by resolution of their governing bodies determine to continue to operate under those agreements until they expire or are terminated. If a governmental entity does not affirm the continued existence of the agreement, it shall expire on July 1, 2004, and this chapter applies. If the governmental entity affirms an agreement, the terms of the agreement and applicable authorizing law will continue to govern activities under the agreement. Mutual aid agreements between Tennessee governmental entities and governmental entities in other states are not affected by this chapter and continue to be authorized and governed by the Interlocal Cooperation Act, compiled in title 12, chapter 9, and other applicable law. Except for the continuation of existing agreements as provided in this section, any new agreements made after July 1, 2004, and aid or assistance provided at the request of TEMA under § 58-2-113, this chapter is the exclusive method for providing mutual aid and emergency assistance between governmental entities.
T.C.A. § 58-8-112