Wis. Stat. § 241.27
Every proposed contract for the benefit of any person, firm or corporation furnishing or supplying in any wise whatever, goods, wares or merchandise to hawkers or peddlers and which by its terms upon execution thereof would bind any person to answer for the debt, default or miscarriage of any such hawker or peddler, in lawfully or unlawfully disposing of such goods, wares or merchandise or the proceeds thereof, or which would bind any person to guarantee or answer for any debt or liability incurred by such hawker or peddler in acquiring any title to or interest in the goods, wares or merchandise to be disposed of by such hawker or peddler or in acquiring any title to or interest in any equipment intended to be used in conducting the business of such hawker or peddler, shall have plainly printed upon it, in red ink, in type not smaller than 10 point boldface type, at the time of its execution and directly above the place for the signature of the person who would, by signing such contract, become obligated to so answer for the debt, default or miscarriage of any such peddler or hawker, the following statement: "Warning - this may obligate you to pay money". Every such contract not containing such statement shall be unlawful and in any action brought upon any such contract in any court of this state, such contract shall be construed in accordance with the laws of this state. The provisions of this section, however, shall not apply to any such contract where the same contains a provision expressly limiting the amount of the liability of each person obligated to answer for the debt, default or miscarriage of any such peddler or hawker.
Wis. Stat. § 241.27