The former CA resident does not have to inform CA DOJ BOF that they relocated and became a resident of another state.
The former resident can voluntarily notify CA DOJ BOF that they moved relocated and became a resident of another state. That way the handgun registration info can be removed from the CA DOJ database.
Notification can be done by mailing in a completed Notice of No Longer in Possession form to CA DOJ BOF.
If the former CA resident visits CA, then it is recommened that the former CA resident does not voluntarily have their handgun registration information removed from the CA DOJ BOF database. Due to the fact that possessing an unregistered handgun is a sentence enhancement and only CA residents can register handguns with CA DOJ BOF.
carrying a concealed registered handgun without a permit = misdemeanor
carrying a concealed unregistered handgun without a permit = felony
Improper transportation of a handgun in CA, can lead to a carrying concealed without a permit violation.
Since non-residents of CA can not register firearms with CA DOJ BOF, any non-resident of CA that improperly transports a handgun can be arrested for a felony.