The politicians who passed the law don't care if the law is enforced, which is why it doesn't matter to them that they don't understand it. They passed the law to get votes to keep their government job with its government healthcare and government pension.
If the cops or prosecutors want to screw with you, the law gives them another way they can do it. I'm reasonably sure that's what Kelly meant when he said he's leaving enforcement to county ASAs. In that sense, registration is truly voluntary. No one actually cares about our stuff. Neighbors, in-laws, and (soon-to-be) ex-spouses are more worrisome.
Meanwhile, no one can buy parts.