does he have a carpeted cat "tree" to climb and play on? If so, he may think any and all carpet is a big scratching post. Can't put that genie back in the bottle. swatting won't do much, but water squirting should. thing is it has to be when he is doing it or VERY shortly after. I'd get some repellent treatment for the carpet from Drs Foster and Mith, online, or from a local pet store.