As our LEO has stated, common sense is the driver in most cases. In all states, it is "generally" interpreted that the front portion of an RV is a vehicle and the part behind that is your house. Search and seizure laws, seat belt laws, Federal Motor Vehicle Safety Standards and other areas generally follow these definitions, but for each case, there are exceptions, and the officer's on the spot evaluation will carry a great sway where the foggy part of the law is sitting. By the same token judge A interprets it one way, and judge B differently, and the officers know which way the judges in his area lean.
Common sense rules. An open bottle of wine in the refrigerator or a half bottle of Jack in the closet won't raise an eyebrow. An open beer can or wine glass in the copilot's cup holder is something else. Again, common sense rules, for the LEO's as well as the RV'ers.