Ariz. Rev. Stat. § 14-5202
The parent of a minor may appoint by will a guardian of an unmarried minor. Subject to the right of the minor under section 14-5203, a testamentary appointment becomes effective upon filing the guardian's acceptance in the court in which the will is probated, if before acceptance, both parents are dead or the surviving parent is adjudged incapacitated. If both parents are dead, an effective appointment by the parent who died later has priority. This state recognizes a testamentary appointment effected by filing the guardian's acceptance under a will probated in another state which is the testator's domicile. Upon acceptance of appointment, written notice of acceptance must be given by the guardian to the minor and also to either the person having his care or his nearest adult relation.
A.R.S. § 14-5202