Write a stern email to your dog asking him not to chew on the couch leg anymore.
Dear Mr. Cody,

I was hoping this issue would be taken care of by now, but it seems you still haven't learned your lesson. You can imagine how disappointed I was to come home yesterday and see new bite marks on the couch legs. 

If this was the first time maybe I wouldn't need to write this email, but this has been an ongoing problem ever since we brought home the new couch. I feel like I can't trust you anymore, which is a terrible feeling for me.

Consider this your final warning before more drastic action is taken (e.g. kenneling, the cone). I have taken pictures of every angle of the couch legs and I'll be able to tell if you even put one tooth into that wood.

On the other hand, if you show me that I can trust you, I might be able to pick up some more Beggin' Strips next time at the store.

I appreciate your cooperation and I hope we can get past this.

Regards,

Your Owner