I'm going to assume, from what you said in your post, that vetoes are handled by collecting a certain amount of votes. If that's the case, I'd tell the owner with second thoughts to either post something on the league message board (if there is one) or get in touch with everyone leaguewide. Let him explain his case and he can ask people to veto. If can muster the votes for a veto, including his own vote, then it can be vetoed. If not, he's out of luck.