I can only speak from my own and a few friends experience, so take it as it is.

If he smokes socially then he still smokes. The only way to quit is to decide you'll never smoke again. My history...

I started smoking the summer before sophomore year of college (late enough that I probably should have known better). I would say for the first 6 months I was strictly a social smoker in that I never purchased my own pack. This eventually crumbled as I started to smoke to relieve stress from school. I would quit for a bit occasionally, I almost never smoked when I was home on summer vacation for example. After graduating college (about 2.5 years ago), I decided it was time to be done for real. The only problem was that I kept making drunk (and sometimes less than drunk) exceptions for social smoking. I would like to say now that I've quit, but it has only been a few months since my last very drunk cigarette. I have to keep the mindset that I'm done for good and there are no exceptions or else I know I will fall back.