There is no "Registration" of firearms in California.
There is absolutely registration of handguns in California regardless of what term they choose to use.
The start of registration went unnoticed by many in California, and since it is done automatically for all new handgun purchases without the knowledge of the owner most residents remain ignorant of it.
Every handgun purchased in California is automatically entered into a state database that is available to LEO and other state officials.
LEO can obtain this information from their in car computers when pulling someone over for a traffic stop, or responding to an address, or otherwise running a person's name who they encounter.
So LEO instantly know the number of handguns registered to a person. I have known people who have been approached cautiously (like an armed criminal) because they had an abnormally large number of legally registered handguns during a routine traffic stop. This identifies them as a "gun nut" to officers which think that way.
(The individual knew that was the reason because the officer asked if they were transporting any of those numerous firearms they were documented as having in the database when the reason for the stop was merely traffic related.)
Every person that moves to California is also required to not only register every handgun they have with the state within 60 days with a "NEW RESIDENT HANDGUN OWNERSHIP REPORT", but must pay a fee for each gun to do it. That fee is currently $19 per handgun.
It even goes further than that. The database automatically cross checks constantly all gun owners and red flags anyone who becomes a new prohibited person for a visit from local LEO. They become an 'armed and dangerous' prohibited person.
In California there is not only felonies, but many misdemeanors which do not make someone prohibited in other states but do in California.
Most of those prohibitions last 10 years, some for life.
Some of those misdemeanors can be discretionarily given in really petty circumstances.
Possession of a firearm as a prohibited person due to any misdemeanor is a felony no different than a felon with a firearm: A felony charge which would then make someone prohibited nationally for life.
Long guns while not registered the same way still have a DROS created. That DROS is supposed to have less information about the firearm, but some stores still add more than necessary in the slots provided.
So all handguns legally purchased or transferred in California since 1991, or which became legally owned in the state by someone moving in from out of state after 1998 are registered in a very easy to search database open to state officials and LEO.
Those which are not registered and legally possessed prior to the law subject people to increased penalties for the same violations of law:
For example a mistake in legal transport of a handgun becomes a felony for the owner of an unregistered (even though legally owned) handgun while it can be only a misdemeanor if the handgun is registered.