I think bark collars should be mandatory on owners. Kind of like the anklets they put on people out on parole. Check in at the campground with a dog, and you have a bark collar put on the owners.
Of course, the collar must be tied into Bluetooth/WiFi/cellular, so it works when the owner is away and the dog left in the RV.
Not sure how many owners could carry around the 55 gallon drum some of them would need for enough spray though.
I could think of some other options other than citronella for the odor........