Many states have a special law that says that if you sell a car to someone and at the time of the sale the vehicle will not pass an emissions check, then the buyer has the absolute right to cancel the sale, and it does not matter if you did not know it at the time. Talk to a local Consumer Law attorney and find out if that is the way the law works in your state. A general practice attorney may not be aware of this particular law but your state motor vehicle licensing department probably is. Call your local Attorney Bar Association for the name of a local Consumer Law attorney or you can look at a National List of Consumer Law attorneys at this web site url address: http://ohiolemonlaw.com/locate-a-local-attorney.html
As you noted in your post, the georgia cleanairforce website clearly states that even if a used vehicle is sold "as is" that the seller is responsible for the vehicle passing the VIR if the buyer registers the car in a county requiring inspection. I am assuming you did not have a prior passing VIR as your county does not require. If the car cannot be returned in the same condition, that may also impact remedies. You should talk to the people as the cleanairforce first and if needed, consult legal counsel.
From the website: Georgia law requires that no person (dealers or individuals) sell a used vehicle, if such vehicle is to be registered in one of the 13 covered counties (Cherokee, Clayton, Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnet, Henry, Paulding, and Rockdale), unless such vehicle has a valid, passing certificate of vehicle emission inspection at the time of sale (DNR Rule 391-3-20-.18(1)). The seller is not required to provide the buyer with a copy of the VIR. Please note: The Georgia Environmental Protection Division (EPD) can only investigate sales that have occurred within Georgia.
There seem to be a number of remedies available, but buying the car back is not absolutely required. Remember however that you can repair the vehicle to bring it into compliance. There are limits on the amount of the repairs and other possible exemptions that may be applicable. More information from the website:
After You Buy
If you are unsure if a used vehicle you recently purchased has a passing inspection on file, click here and you may search via the vehicle identification number (VIN) for a free copy of the Georgia Vehicle Emission Inspection Report (VIR).
If you purchased a used vehicle that did not have a passing VIR at the time of sale and the seller (dealer or individual) refuses to comply, you may request an investigation by the Georgia Environmental Protection Division (EPD). If you wish to file a complaint, complete the Used Vehicle Sale Complaint Form. Complete the form and mail to GCAF (address included on the form). A representative from GCAF will contact you once the case has been reviewed.
EPD will not represent the complainant in any legal matter nor will EPD negotiate a vehicle buyback or repair settlement between the buyer and the seller. EPD will handle each complaint separately and will consistently administer its enforcement policies and protocols. Any legal action between the buyer and seller is independent of enforcement actions taken by EPD.