Welcome to the US government where government bureaucracy has confiscated our rights and selling them back to us one license and permit at a time...
The irony of this is that you can build and
register your own vehicle that likely wouldn't be as safe as a mass produced product like side by sides. I suppose the justification is that in exchange for not having to insure ATVs and UTVs like highway vehicles we agree to keep them on the dirt. Nominally I'm okay with that justification but I think there should be more leeway than there already is.
As an example, I was camping this summer at a lake and there were offroad trails accessible just a half mile down the road. We took the risk and just drove our ATV and UTV down the road to the turnoff fully expecting that should an officer spot us, we would have to be trying to talk our way out of a ticket. In that particular area though I have to think that most cops really wouldn't do much more than a verbal warning unless they were particularly cranky that day.