Ariz. Rev. Stat. § 13-3872
Any two or more public agencies as defined by section 11-951 having and maintaining peace officers may, by action of their respective legislative or other governing body, enter into mutual aid agreements with respect to law enforcement provided mutual aid agreements entered into on the part of the state of Arizona shall be approved by the agency involved and the governor. A peace officer acting within the jurisdiction of any other public agency pursuant to a mutual aid agreement shall have full authority to act as a peace officer to the same extent as if he were a duly appointed, qualified and acting peace officer of such public agency as herein defined. Mutual aid agreements provided for in this section shall be entered into pursuant to the provisions of title 11, chapter 7, article 3.
A.R.S. § 13-3872