I have also seen this enforced at uwharrie...just an FYI.
Anytime on OR CROSSING a state maintained road (asphalt or not) must have tags, registration, ins, etc. (I.E. must be street legal)
Now a good friend owns a used car lot and frequently uses temp tags(once had 7 t4emp tagged rigs in 1 caravan into Murphy), which are covered under the dealer's insurance etc. I'd hate to fight that one but I guess technically it would work.