Linda Perlis suggests that to legalize cannabis might encourage teens to become the new drug  pushers of the future. And I assume for that reason  she is of the opinion that prohibition should be continued.
If this is sensible, then a logical corollary would be to add alcohol and cigarettes to the list of prohibited substances in Canada.  To save our youth from what already must be irresistible forces to become bootleg criminals. 
Or perhaps she is just suggesting this will be one of the down sides. But would it be a downside for their peers to be accessing cannabis no longer contaminated with mould, or laced with fentanyl. And by not buying cannabis from gun wielding Hells Angels, are we sure this is an overall "negative"