One idea that springs to mind: if a person starts up an anonymous, online marketplace for that activity, imprison him forever.
I don’t personally hold the opinion that Ross Ulbricht shouldn’t have been pursued according to the law- or support his pardon- or even that darknet drug markets should exist! I’m also not really interested in crypto.
However I strongly believe that a completely different approach to drug laws & regulations is necessary to make people safer and reduce crime.