Since you sold it on craigslist, the copy will remain on your account for quite awhile. I would say since you sold it in this condition stated in the ad, he got what he wanted. He BOUGHT a vehicle that he KNEW wouldn't comply, but is now trying to get something he didn't buy. If your ad stated it was as is, and had these mods done to it, then I would say he got what he wanted. Now he is in a bind and trying to get something he didn't purchase. On the other hand, depending on state/federal laws. your on the hook for removing emissions equipment. So it's a catch 22. Now if you had sold it as an off road use/race vehicle, he would be up a creek. Since you sold it for road use your on the hook for the emission laws.