First, he has committed a major criminal act. Second, you have come out with all your defence for your "friend." How are you so sure he smoked this drug "only two times" and not more or less number of times and that too "mistakenly". Ha! Ha! You also claim that he "never sell or support that drug." Try telling this story to the judge. See his reaction and if he gets convinced.
Your "friend" is in real hot waters for "just smoking marijuana" as you have described it as if it is not a serious crime. Surely he must be having the right links to get hold of this illegal item.
If you wish to know what action will be taken on him, suggest you talk to the police authorities or a lawyer.