Benjamen Franklen Gussen (University of Auckland) has posted The State is the Fiduciary of the People on SSRN. Here is the abstract:
A fundamental legal relationship exists between the state and each person subject to its authority. This overarching relationship is fiduciary in nature, and arises from the fact of sovereignty under the rule of law, with which comes the authority to establish legal order, and from which flow the power to legislate, administer, and adjudicate. This relationship has the general features of trust, authorization, and discretionary power that one typically finds in fiduciary relationships. The free-standing public duties of legality, (procedural) fairness, and reasonableness may be justified and understood as public fiduciary obligations.