You can do so but it is more of a safety issue if anything. There are no hard rules although many tend to believe there is, wishful thinking I guess. It seems that there are trips each year where we have had to overnight in a Walmart parking lot a time or two.
We pull into WM pretty late and find a place to park, either among other RVers or off to one of the edges. In either case we deploy and use whatever we feel inclined to do including slide-outs, stabilizers, and onboard generator.
Since we always need something we will do a bit of shopping before we go to bed in order to make a quick getaway in the morning. Obviously it would not be wise to bring out a bunch of chairs and start the barbecue under the awning , these kind of stops are to get some sleep and maybe stock up for the trip.
