What will happen?

I don't think they would have problem with any public run campground. Private campgrounds sometimes have age and rig rules, but honestly you don't see it enforced often. When there's empty sites, those campgrounds get less picky about where the money is coming from. The only ones that are really strict are the expensive and glamorous campgrounds, but college kids traveling the country probably aren't looking to stay at these campgrounds anyway. I wouldn't imagine that they would have a problem with overnighting at a Walmart as long as they're overnighting. Walmart isn't particular about the type of vehicle. Half the time you see big rigs clogging up the parking lot.