Here's a curve ball question: can a California cop issue a citation for no front plate to a visiting out of state registered and licensed car that is supposed to have a front plate but doesn't?
I don't believe so, as the car complies with the state regulations where it was registered; and the states have reciprocal agreements. Similarly, an out-of-state car does not have to comply with CARB specifications. If the car is being constinuously used in California, they may investigate and require the car to be registered in California, as there is a grace period to have a car registered to a permanent or transferring resident.
From the California DMV:
When fees are due
Fees must be paid within 20 days of entry or residency to avoid penalties. Any vehicle owned by a California resident must be registered within 20 days of entry into California unless a special permit was obtained.
Nonresidents whose vehicles are properly registered to them in their home state or jurisdiction may operate their vehicles in California until they:
• Accept gainful employment in California.
• Claim a homeowner's exemption in California.
• Rent or lease a residence in California.
• Intend to live or be located here on a permanent basis (for example, acquire a California driver license, acquire other licenses not ordinarily extended to a nonresident, registered to vote).
• Enroll in an institution of higher learning as a California resident or enroll their dependents in school (K-12).
http://www.dmv.ca.gov/pubs/brochures/howto/htvr9.htm