Long guns are not registered and the serial numbers are not put on the firearms transfer forms. Handguns are not FORMALLY registered, but are defacto registered on the firearms transfer forms, which are supposed to be destroyed.
If the forms were destroyed as required by law, then we would not have this defacto registration. Since the forms are kept by the firearms dealers forever, as required by BATF (in violation of the law), California state has a defacto firearms registration.
You better believe it. If a California gun is stolen and turns up in a crime, you better believe that it will be traced back to the original purchaser this way. That is registration.
And those permanently kept records can be used for gun confiscation.
As for long guns, there is no defacto registration. When the California AG went to confiscate SKSs, they could only find those from people who sent in registration forms for guns that California mis-labelled as “assault weapons”.
They are in Oregon and, I've heard, Illinois. Oregon does it's NICS through the State Police.