wow, absolutely ludicrous.
I work for a business that advertises, and allows the public onto our property to do business. Just because we are a business, it is still privately owned, and private property. Just like CC said, if a LEO wanted to come snoop around, I would tell them to GTFO. Ever been in a Bar, and seen the sign on the wall that says "we reserve the right to refuse service to anyone"? its there, because the bar is private property, even though it is a business. There are some exceptions, such as fire marshal inspections and whatnot, but the idea that the state could require someone to have an ORV permit, or even SOS plates on private property is a joke.
Its like running off road diesel in your truck on private property, perfectly legal until you put a tire onto a public road.