They don't need rules, a board meeting, or even a real problem. All they require is something parked in a driveway that does not match their personal vision of correct, and the neighborhood has become a danger zone that demands official attention.
This is the same brain that calls the city because a lawn looks two inches too tall, or reports a house because a truck sat in the same spot for an entire afternoon. Their issue is that somebody made a choice without submitting it for approval first. A camper is just a vehicle, but to the right kind of neighbor it becomes evidence that standards are slipping and something must be done before the whole block turns into a travel park.