Do you Need fenders on trailers in Wisconsin?

According to the Wisconsin Department of Transportation (WisDOT):

All trailers or semitrailers, except boat trailers, having a gross weight of 5,000 pounds or more, shall be equipped with rear fenders.

If the trailer or semitrailer is constructed with solid side panels having a vertical height extending to the floor, or with a body, side panels, or doors that enclose all wheels and tires from the ground up, fenders are not required.

Also, fenders are not required on trailers and semi-trailers manufactured or initially purchased before March 28, 1997.