The rule is the same wherever a person moves in the United States. If a person move states permanently, they will need to check in with the DMV to take care of a few changes, like drivers license and car registration. If they do not do this, they risk being cited by the police if and when they are caught.
If you have any friends or family moving to California permanently, they will need to get their license or identification card updated with a new local address within 10 days of moving. If there is a teenager who currently has a driver permit, this will also need to be updated. It is a good idea for your loved one to get familiarized with our driving and safety laws, because not all driving laws are the same in each state. For example, turning right on red is legal here in California, but it might not have been allowed in the state they came from. Where they came from, maybe they were allowed to use their phone while driving, but here in California, it is against the law.
Your loved one will need to register their vehicle within 20 days of establishing their California residency. In order to do this, they must have valid car insurance. Then, a smog and emissions inspection is required for the vehicle.
A person can be cited and ticketed if a police officer discovers that they have been living here in California and driving around with their old license and registration. Even if the old license has a later expiration date, it is not valid here in California because they are now supposed to hold a California license.