Some good new for 2017! :D

Black market. Ivory just becomes more valuable when there's less of it. And there'll always be demand too, especially in china

Yeah, but that's the black market, which most people don't use. I'm not saying it's going to become a complete thing of the past just by banning it, but not a lot of people are willing to go to jail over some horns. Like if they made certain types of lipsticks or a certain vegetable illegal for some reason, yeah some people will still want it, but it's not worth the trouble for a lot of people so use of it will go down somewhat.

Drugs are illegal. People still get their hands on it easily, but would it be a good idea to make it all legal?

It's easier for regular people to buy ivory if it is sold at the pawn shop or jewelery store.

Because people can make drugs. Like during prohibition people would make alcohol themselves. You can't go and hunt ivory yourselves unless you go to like Africa, and even then if it's illegal you won't be able to bring it back or sell it unless you had the money and means to sneak it back in.