oh... this is extreme -- but I have heard it can work to drive out the smell of cigarette smoke. Ammonia fumes- find a way to suspend the case in a container above some ammonia. Don't let the ammonia wet the case. Just the fumes, about a day or so.
The Ammonia evaporates rapidly so hang it out to air on dry day. Then use a non oily, non waxy leather lotion. The leather will need it afterwards.