Any body else seen this new law change in WI, for out of state riders. It just went into effect on april 20, 2004.
This website describes the changes.
new Wi atv rules


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Non-Resident ATV Trail Pass
This one is the biggie! A new Non-resident ATV Trail Pass is being implemented in Wisconsin. All ATVs that are registered outside of Wisconsin will be required to visibly and permanently display a Non-resident ATV Trail Pass on the forward half of the ATV. The Trail Pass will cost $18 and will be available through any license agent (ie where you would purchase hunting & fishing licenses, etc…). Illinois and Michigan ATVs (as well as any other ATVs without registration in their home state) must be registered in Wisconsin, in addition to purchasing the Trail Pass, until additional changes can be made to the legislation to simplify the matter. "