It's actually not as silly a remark as one might think. California has been in the vanguard of smog control, and some of the big cities have had Smog II imposed on them, because of a combination of factors not necessarily found elsewhere: large population concentrated in smog-bowl geographies with a car-intensive culture and an atmosphere (no pun intended and not much of one achieved) wherein quite a bit of environmental regulation is tolerated or even embraced or at least grumblingly put up with.
Over the years, many a vehicle that failed to pass California smog, or was too much of an expense and hassle to keep in compliance, has migrated to a less populated, less regulated, better ventilated, or more pollution-tolerant place. Doubtless this phenomenon has benefitted from proliferation of Internet sale and auction sites.
It isn't just cars, incidentally -- a lot of sources of the various kinds of air pollution come under regulatory scrutiny in California, especially in cities that have high population and geography and weather that tend to concentrate smog.
Best of luck,
--Joe