Yeah I have to agree with pdx. I have dealt with many local, state, and county regulations over the past 3 years I have been a vendor here in Texas.
You have to research these regulations prior to buying your cart. Different municipalities within the same county will all have different ordinances. You have found this out after purchasing your cart. The April 1st ordinance sounds unusual too me here in Texas, however it must be related to the with long winters there in Wisconsin.
Maybe chicago style will have a few comments since he in Wisconsin also.