I don't think this is the right question, since it implies that smoking is "permissible". For reasons I have gone into at some length, I do not see how smoking can be properly seen as being anything other than sin. So I do not see how it is even "permissible". The addiction dimension should, of course, fill us with compassion for the smoker. But its still sin. We would not say that a person who is addicted to promiscuous sex is not sinning simply because the person is addicted, would we?.