I don't know exactly what the law I, but I do know our snowmobiles are registered at the DMV and have to have titles like a car. They're not registered with the forest and need no title like a dirt bike where you can just register it at a dirt bike shop.
We can ride the roads with DNR sticker and insurance card, valid drivers license or a safety course if between 12-16 as long as:
Headed to the nearest trail or gas station
Going the same way as traffic
Stay 10 ft from the road when possible
Obey posted speed limits - most towns post for snowmobiles
Most towns (there all small) have routes through them, with option for gas and food.
Groomed trails (or ungroomed trails) across private land is all maintained by club members, including bridges, crossings. No speed limits, so 100+mph welcome :D