The legislature intends that the retirement plan is a qualified pension plan under section 401 of the internal revenue code, as amended, or successor provisions of law, and that the trust is exempt from taxation under section 501 of the internal revenue code, as amended. The assets of the fund are held in trust for the exclusive benefit of the members and beneficiaries of the retirement plan. The board may adopt such additional provisions to the retirement plan as are necessary to fulfill this intent.
A.R.S. § 38-900