I don't know. He's been thinking about leaving for quite a while.
At one point, he removed the CBK tag and went around tagless for a while, apparently "to see what it was like", but I have my doubts... I honestly think he's been looking around for another clan.
It's up to him, but I don't know if I would let him back in, if he ever decides to return (or try to, for that matter).