(1) The intrastate mutual aid system is established to provide for mutual assistance in an emergency among political subdivisions and federally recognized Indian tribes that choose to participate as member jurisdictions.

(2) Except as provided in subsection (3) of this section, member jurisdictions of the intrastate mutual aid system include:

(a) A political subdivision; and

(b) Any federally recognized Indian tribe located within the boundaries of the state of Washington upon receipt by the department of a tribal government resolution declaring its intention to be a member jurisdiction in the intrastate mutual aid system under this chapter.

(3)(a) A member jurisdiction is released from membership in the intrastate mutual aid system established under this chapter upon receipt by the department of a resolution or ordinance declaring that the member jurisdiction elects not to participate in the system.

(b) Nothing in this chapter may be construed to affect other mutual aid systems or agreements otherwise authorized by law, including the Washington state fire services mobilization plan and the law enforcement mobilization plan under chapter 43.43 RCW, nor preclude a political subdivision or Indian tribe from entering or participating in those mutual aid systems or agreements.

(4) Mutual assistance may be requested by, and provided to, member jurisdictions under this chapter for: (a) Response, mitigation, or recovery activities related to an emergency; or (b) participation in drills or exercises in preparation for an emergency.