I'm trying to understand why people would need fully automated high-power assault weaponry that are capable of killing a multitude of Humans in a matter of seconds.
Even the police don't have full-auto weaponry that some Citizens are now legalized to have.

So why exactly do people need it? There's no reason to have such a weapon, save if you're just a collector. Which, in my opinion, means you should be exempt from the ban so long as you can have some manner of proof that it is for collection purposes and not firing.