An e-mail, not from a mom yet:

Not wanting your child to smoke is a separate issue from profound concern that if your child does smoke, he or she will happen to do so at the party that will happen to be busted, resulting in a juvenile or criminal record that will put paid to much of the child’s future hopes, options, aspirations.
The legalization issue turns on which set of dysfunctions we want to countenance. But in a free society, and so long as the substance isn’t addictive (which of course robs us of freedom) the bias must be toward liberty.