Wis. Stat. § 78.47: Alternate fuels license.

No person may act as an alternate fuels dealer in this state unless the person holds a valid alternate fuels license issued by the department and a valid certificate under s. 73.03 (50). Except for alternate fuel which is delivered by an alternate fuels dealer into a fuel supply tank of any motor vehicle in this state, no person may use an alternate fuel in this state unless the person holds a valid alternate fuel license issued by the department or unless the alternate fuel has been delivered by a supplier who is authorized under s. 78.40 (1) to report and pay the tax on behalf of the user or retailer.