Wis. Stat. § 344.16
The uninsured motorist coverage requirements of s. 632.32 are inapplicable to self-insured entities under s. 344.16. Classified Insurance Co. v. Budget Rent-A-Car Inc. 186 Wis. 2d 476, 521 N.W.2d 478 (Ct. App. 1994). No statute requires a self-insured entity under s. 344.16 to provide uninsured motorist coverage as part of the optional insurance it offers to its customers. Prophet v. Enterprise Rent-A-Car Company, Inc. 2000 WI App 171, 238 Wis. 2d 150, 617 N.W.2d 225, 99-0776. A car-rental company issued a certificate of self-insurance under this section and subject to liability limits under ss. 344.01(2) (d) and 344.51 was not a self-insurer for purposes of an underinsured motorist clause that excluded coverage for a vehicle owned or operated by a "self-insurer." Bethke v. Auto-Owners Insurance Company, 2013 WI 16, 345 Wis. 2d 533, 825 N.W.2d 482, 10-3153.