I've been reading up on Idaho regulations but the only thing I can find is this from https://parksandrecreation.idaho.gov/activities/atv-motorbike:

Any person without a valid driver's license who wishes to operate an OHV on US Forest Service roads must take an IDPR-approved OHV safety course and carry their completion certificate while operating their OHV.

It just says you need a valid driver's license or take a safety course but I'm not finding anything about the vehicle being licensed for street use. Do you have a source or website with that? I'm not trying to argue but am trying to make sure I get things right. This place has been considerably Californicated in the last 25 years and even back then every Fish cop, Park Ranger or part time tour guide out there was just itching to bust you for some minor infraction.

Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!