I personally think you should step away as much as possible. If he is really ready, he probably does know the ropes, especially after being in jail. Inmates learn a lot from each other. If he isn't ready, then nothing you say or do will help anyway. It will just frustrate you.
I now try not to talk to my AS about his doing/not doing drugs as much as possible. I 'try' but am not always successful at just talking about it if HE brings it up. Occasionally I do ask him for basic info about his situation but I am really trying, at least, to leave this up to him. Not easy sometimes though.
I would write back and say. "Okay, I was just wondering." Then go on talking about other things that are not drug related.
Kari