It is actually a dedicated post office facility, it has its own entrance from the sidewalk and the normal signage on the doors and windows. I wouldn't think they would be able to enforce it there, but you never can tell, the law seems too vague in this case.
Yeah, if I were a Walgreen’s customer and someone with another business in the same center tried to tell me what I could or could not have in my car, I wouldn’t take to kindly to it.