Don't underestimate people.
Prohibit something that people like or somehow need, and they'll go there where you don't have much oversight as government to get it.
It seems countries never learn this. The era of Prohibition in the United States was a big example. It was all the banning of things that created underground empires and lords.
I agree some things should always be banned but when talking about something people desire, and telling them they can't do it? What happens to children when you say they can't do things? They do them anyway but they hide it from you.