Exactly, what the heck are they gonna do if you just drive over it? Tell you off? Call the cops? lol

On the serious side though, I've never seen any bad 4wd dune damage down there (apart from me setting fire to my van, but we won't dwell on that..)
Yes we drive up the dunes to park within sight of the water, but generally only in areas where the grasses have been washed away by storms anyway.