Much like marijuana. Prohibition only made the product even MORE sought after, and a large illicit market grew up, fueled by a typical degree of rebellion and flouting of the law.
Legalize it and tax the hell out of it.
And regulate it. Allowing vaping products to be sold at every convenience store is what created this mess. The time for restrictions was at the outset, when no data existed. Requiring a prescription from a doctor is all it would have taken, after all they are a delivery device for the highly addictive drug, nicotine. Any adult wishing to use them would have been able to do so, but not kids.
Legalize it and tax the hell out of it.
Taxing the hell out of it allows the illicit market to remain large. Tax it enough to pay for the regulation enforcement and education that will discourage use.