I say inform his parents or an authority figure..
Hashish is not a hard core drug but chances are if he is doing this, he is doing other things on the side.. this is a downward spiral .. very few people come off of it..

Hasish isn't addictive, it will just do away with his mind, and if his base line is stupid which I suspect it is for doing drugs to begin with, then he'll be so fried he won't even be able to bag groceries at tesco and I know in England they leave the bagging to the customers anyway so really he is looking at wiping cars, or cleaning toilets with no prospect of improvement?

it is his choice, you can only offer advise or be pro-active in getting some authority figure in to help him out..

p.s excuse my judgement of the fellow... I have very low tolerance for self-imposed stupidity..