Wisconsin Info Needed

[EXNODRAMANOTCH]

Does anybody here know the laws/rules in regards to a civilian driving a retired police car in the state of Wisconsin (or where to find the info). I talked to a guy at a car show this weekend who claims that all marked police collector cars must be trailered in Wisconsin and not driven on public roads. This could be a problem for me as I like to go to a couple of shows in WI, and I plan on storing my SSP in WI next winter (and I don't own, or want to own a trailer). I can't find any info on this on the internet. Thanks for your help!
Bob