[w-ll]

Just like alcohol use crashed with prohibition, or the drug market? Previous attempts to stop these have resulted in larger market shares of those willing to still do related business and almost always increases demand.

[ufo]

Illegality doesn't increase demand. It just means that the supply gets provided by shady criminals instead of legal business that follow the rules.

[erikpukinskis]

It increases the per-vendor demand as experienced by the vendors who stay in the market.