Total guess, but I imagine the penalty is similar to using any other motorized contraption. And I know from personal experience that it can be harsh. Story time....
Close to 20 years ago I bought my first pickup truck. It was a 1990-ish Toyota pickup from before the Tacoma days. Fun truck to drive around in the mountains. One night we were exploring roads in the foothills near Smithfield, Utah. We followed the road up over a ridge and then it started descending down the other side. It started getting really faint like an ATV track as it descended a steep hill. I tried to back up and couldn't make it and ended up getting stuck sitting at a really awkward position on a steep hillside. The truck was stuck at such an angle that you could have given it a big push and probably sent it tumbling down the hill. We hiked out so that we could recruit someone to come back and help pull us out.
It rained hard the next couple of days and so we had to delay going back for it. I was worried about the soil getting soft and the truck tumbling so I hiked in with a tow strap and hand winch to secure it to a tree until the roads dried out enough to retrieve it. When I got there, there was a note from the forest service telling me to call them before attempting to remove it. I called when I got home and they informed me that I had driven through the Mount Naomi Wilderness to get where I was. I was no longer in it, but the road out cuts back through the edge of it. I apologized and explained I was following a well worn road until it petered out. They told me that that doesn't matter, that I should have a map and know where I am. I asked them why the road wouldn't be closed or have signs. They said there have been signs in the past but people take them down.
They then informed me that there would be absolutely no driving in to get it. There wouldn't even be any driving out if I were to get it un-stuck myself. I would have to use horses and disassemble the truck to pack it out of the wilderness. Unless of course I could convince congress to allow an exception to the rules. That wasn't going to happen. We went back and forth on this and got nowhere.
So the following weekend, we went in and got it despite their instructions not to do so. I had a friend drive me in and we winched it out and drove away. A few days later the forest service and several members of the Cache County Sheriff's office showed up to my work and requested I come outside. They demanded I tell them who helped me get out. They explained I would be facing multiple charges and so would the person who helped me. The sheriff was in my face, pushing me into a car, yelling at me, telling me they'd throw me in jail until I talked like I was a serious criminal. An obstruction of justice charge was threatened. I called my friend and explained the situation and ensured him I would pay for all of his fines and legal bills if he would let me disclose his identity. He reluctantly agreed.
A few days later the forest service contacted me and informed me I would be getting three charges for driving in wilderness. One for each time I supposedly crossed the line, as would my friend. Somehow, my friend was never charged. I ended up in federal court in Salt Lake defending myself. The defendant who was up before me had literally been charged with killing a bald eagle. I explained the situation to the judge. The maximum penalty was going to be $30,000 in fines ($10k per charge) and I think up to a year in jail per charge. The judge was kind and reduced it to the minimum fine of $100 each. He put me on probation for 3 years where if I committed any other kind of 'watershed violation', all of it would have come back and I would have received the max penalty. Such a crazy experience. And I absolutely love the wilderness. I spent a ton of time in the Naomi Wilderness at the time and I would defend it vigorously. On any given weekend there would be streams of 4x4's and ATV's going on the same road without penalty but because I got stuck...
