If he puts up such a fuss when it is time to leave your Mother's fireplace, either leave him for her to keep since he seems to like it there so much, or don't take him to visit her anymore, explaining to him that this is what GROUNDED means for kitties that behave inappropriately.
Be sure you are stocked with plenty of bandages and gauze before laying down the law. Denying a cat fireplace privileges is risky business! :p