Per the DMV the seller is required to obtain a smog certificate prior to the transfer of title to the vehicle. No smog certificate, no transfer of title.

I believe that current and valid registration is sufficient, but it may be only so long as the vehicle was smogged in the past year. I recently sold a car to a friend of ours and we did not have to get it smogged ... though it had to pass inspection several months earlier for registration renewal.

So ... who has the car right now? Have you gotten it back? If not, then if there has been no transfer of title or release of liability filed, you might just be able to go collect the car yourself as it is not legally his.

- Carl