Ariz. Rev. Stat. § 48-2336
A. The board shall, for and in the name of the district:
5. For the purpose of acquiring a supply of electric power to serve the customers within the district's service area, the board, for and in the name of the district, may acquire, own, lease, construct, operate, equip and maintain or contract for, severally or in common with others, electric generating and transmission facilities without the boundaries of the state, or to contract for a supply of electric power without the boundaries of the state. All of the powers in this paragraph 5 are subject to the following limitations: