Ariz. Rev. Stat. § 6-386
In the absence of an express provision to the contrary, if an indenture or other governing instrument directs, requires, authorizes or permits investment in United States government obligations, a bank, trust company, trust department or other fiduciary may invest in the obligations, either directly or in the form of securities or other interests in any open end or closed end management type investment company or investment trust registered under the investment company act of 1940 (54 Stat. 789; 15 United States Code sections 80a-1 through 80a-64 ) if the portfolio of the investment company or investment trust is limited to United States government obligations and repurchase agreements fully collateralized by United States government obligations and the investment company or investment trust takes delivery of the collateral for any repurchase agreement either directly or through an authorized custodian.
A.R.S. § 6-386