I'd say, where possible, you have to give half a metre. The reason I raise this query now is some old bastard was literally stood on my shoulder during a cigarette transaction earlier today.
He was clearly not up to anything and was smellingof booze so probably not aware of his faux-pas, but nevertheless...he has broken one of the golden rules of being a human and was told so - in a controlled and non-threatening manner, obvs.
I expect no replies