Your are correct in terms of the seller of a vehicle being responsible for providing a Valid smog check certificate during the sale of a vehicle; seen in Section 24007 (b)(2) of the California Vehicle Code. There is no provision in the law to sell a vehicle "as is" in reference to the emissions test.
You have the option of paying for the smog repairs this Volkswagon Passat needs in order to pass the smog check however you might end up having to take the seller to small claims court to recover your cost if the seller does not cooperate. Although the law clearly supports you as the buyer, collecting on a small claims judgment can be difficult, so the amicable solution is usually best.
