In Kalifornistan, any handgun you buy is automatically registered to you, and that information is kept permanently.  The police department in my suburb were able to show me all of the handguns I own on their car computers, including make, model, and serial number (this was at my request, BTW, as I was curious, and know a couple of local cops).  Any officer here can pull this info up virtually at any time for any reason.

-Troy