Create a black market? A black market already exist and is in full force.
Fair enough. You are correct. "Dramatically increase the demand and supply on the black market" is a better way to say it.
The reason I think the demand will grow is you now have a much larger clientele for guns. Instead of lets say a million people looking to buy black market guns you have 30, 40, 50 million... looking to buy a firearm.
Not to mention those that come up with a home made work around...