Non-California vehicles in California

There’s a model of Vespa, and the Royal Enfield motorcycle that are not sold in California (presumably because of California’s emissions laws).

I’m now living in Washington, but am planning to move back to L.A. If I were to have one of these vehicles, would I be allowed to take it to California?

Wouldn’t it have to eventually have to pass emmission inspection?

AFAIK motorcycles do not have to have smog tests (though they apparently do need to meet emissions regulations before being sold in California).

This site says:

Is the model you’re looking at new (being defined as haviung less than 7500 miles)?

Aha! From the link:

So if I were to buy one of these motorcycles (which I’m not planning to BTW) and register it here before I move back, then I could take it with me.

Thanks.