What is your mechanism for banning them? Other than "passing a law".

But you ban a lot of things by passing laws. You ban speeding by giving fines and jail time, you ban alcohol in public (some places) by passing laws and enforcing them, you ban someone from flying drones near airports by the same. Some people still do these things of course but the law and strict enforcement certainly reduces the amount of speeding, sex in public and the number of drones flying near airports.

Why would it be so different for guns?

You could also go after the gun manufacturers, offer incentives to turn in guns before imposing penalties etc. You can then go after firing range owners who allow certain guns on their premises.

You just have to want to do it, and the real problem, no one wants to try.