You don't think people who are willing to break the law this way won't just manufacture them?
If that is what you're saying (and please, clarify if it's not!) - it's worth knowing that both Wisconsin and Indiana are a 90 minute drive from Chicago city limits, so any illicit manufacturing has to compete with the ease of a relatively short drive to purchase in another state.
I think sometimes people forget just how close Chicago is to other states.
So the argument that Chicago residents can skirt gun control laws by crossing state lines is false.