Tabin: you fight the good fight, my friend, but this law is a chaos factory. "Several doses" of heroin for a first-time user is a fine ticket for a round trip ride on the midnight train, more than enough to teach a man how to ride a horse -- all the way to town. His eventual addiction will outpace, outlast, and finally outsmart even the Mexican government.
The law will, by then, have succeeded only in delaying the smack-fueled crossing of its redrawn line in the sand. Which, I suppose, has its appeal when one's too busy trying to keep cops from going crooked to keep kids from getting bent.