As everybody else has stated, you need to check as to the legalities within your locale. I would suggest talking to a state patrol officer of rank. It is their job to know traffic laws. You also need to realize that you need to be legal in whatever location you go to. Whereas my Class D (regular license) on a vehicle licensed as an RV is legal, even in states that require an air brake endorsement for RVs because there is no equivelent available to me, with alcohol related laws, the same is not true. I know it's not legal for passengers to be drinking in Minnesota, North Dakota, South Dakota, and Wisconsin. It is, however, legal in Montana.
In Minnesota you can cirvumvent the regulations, but it's not easy. It has nothing to do with this walled off passenger compartment that everyone I've talked to here in the state seems to think is legal. Instead, the driver must have a commercial license with a passenger endorsement, most likely a Class C. The vehicle must then be registered as and insursed as a commercial vehicle. This includes being subject to various state inspections and obtaining a DOT number. You must also be operating as a commercial vehicle if your passengers are drinking. It is not enough to simply be a commercial vehicle with a commercial license. You need to have documentation showing that you are currently operating as a paid driver. You are then subject to commcercial alcohol related laws meaning a DWI is now at a .04 BAC and if you have ANY alcohol in your system you will be red flagged and parked for 24 hours. Yes, one drink is too many.
Complicated, eh? That sazid, I will admit that I have had passengers drinking while I was on the road before. I, of course, was not. The general thought process was that open bottles are legal as long as they are not within easy each of the driver (open beer cans would raise question, however) and as long as they are not currently being used by passengers. We were really countin on not being pulled over and with good reason. Simply put, there was no reason for it to happen. On top of that, a law enforcement officer would have to make a fairly long walk to get to the front door on the vehicle and I assure you all drinks would have ben gone before he got there. Drunk passengers are not illegal.
As a sidenote, I also talked to an officer about the whole search warrant thing. As a recreational vehicle parked at a campsite an officer needs a search warrant to enter the vehicle aside from cases of emergency. This is no different from a house. However, if the vehicle is operating as a motor vehicle, motor vehicle laws apply. UIf you get pulled over in Minnesota on the highway in your RV you are subject to the same laws as if you were in your car. The officer simply needs reasonable cause to search your vehicle. The definition of reasonable cause varies by the judge you'll be seeing in court, but precedent in Minnesota has gone so far as to say that eating while driving or having cigarette rolling papers, even with tobacco in the same vicinity is reason enough. Regardless, a police officer is not allowed to ask if he can search your vehicle. He/She needs to either do it or not do it. Precedent in the state has shown asking to be a form of entrapment. You're damned if you say yes (and actually have something to hide) and you're damned if you say no (what might have been a warning turns into a citation because you weren't "cooperative").
All I can say is that knowing police officers and lawyers and having hypothetical discussions with them has been incredibly helpful and interesting. I pride myself on being legal 99.9% of the time, but it's always good to know the what-if's.