Banning Ivory, or anything for that matter, and thinking it will stop it's import, sale, and distribution is a lot like thinking legislation will win the drug war. Problems like this need to be solved at the source, and like drugs, we cannot control the sources outside of our borders, and try as we do, we simply don't have the resources to keep it from coming in. The other solution is to stop the demand, but that's not likely to happen either as people want what they want, and justify it anyway they can.
New "laws" seldom solve a complex problem, but simply make the masses feel better as well as give politicians a way to claim effectiveness in office.
Seems to me a ban on Ivory will merely drive up the cost, and consequently increase the poaching due to greater value.