I do not expect this to survive five minutes into it's first court challenge. All that's needed is proper ID of the seller, much easier than following a check through half a dozen parties without reasonable doubt torpedoing a case.
Obviously it's not about metal thieves, it's about statist tyrannical control.
I hope you are right. I also hope people are standing in line to challenge this in court.
If it survives in LA, we can look for other states to try similar nonsense.