Wis. Stat. § 18.62: Revenue obligations as legal investments.

Any other provision of law to the contrary notwithstanding, any of the following may legally invest any sinking funds, moneys, or other funds belonging to them or within their control in any revenue obligations issued under this subchapter, which shall be authorized security for all public deposits:

(1) The state, the investment board, public officers, municipal corporations, political subdivisions, and public bodies.

(2) Banks and bankers, savings and loan associations, credit unions, trust companies, savings banks and institutions, investment companies, insurance companies, insurance associations, and other persons carrying on a banking or insurance business.

(3) Personal representatives, guardians, trustees, and other fiduciaries.