the interpretation of the statute has clearly been vested by a provision of law in the agency’s discretion. See Iowa Code § 17A.19(10)(c), (l). If the agency has been clearly vested with interpretive authority, we generally defer to the agency’s interpretation, and may grant relief only if the agency’s interpretation is “irrational, illogical, or wholly unjustifiable.” Id. § 17A.19(10)(i). If the agency has not been clearly vested with discretion to interpret the statute, “we are free to substitute our judgment de novo for the agency’s interpretation and determine if the interpretation is erroneous.” Auen v. Alcoholic Beverages Div., 679 N.W.2d 586, 589-90 (Iowa 2004) (citing Iowa Code § 17A.19(10)(e)). The legislature has delegated broad authority to 643 N.W.2d 205, 207 (Iowa 2002) (<HOLDING>). Section 147.76 clearly'vests the board of
holding board cannot ignore the rules it adopts under the delegation of authority to prescribe rules for its governance and the governance of the university because such rules have the force and effect of statute holding grant of authority to an agency to adopt rules necessary to carry out this chapter clearly vested in the agency authority to interpret a statute holding that director of police department does not have final policymaking authority in miamidade county despite having some discretionary authority holding statute providing the director shall have the power and authority to prescribe all rules not inconsistent with the provisions of this chapter necessary and advisable for its detailed administration and to effectuate its purposes vested authority in the department of revenue and finance to interpret section 4224520 holding that congress had exceeded its authority by using its section five power under the fourteenth amendment to enact the statute