Unfortunatley, not much. Yahoo won't do anything. If he hasn't locked you out you can Email League and you can all Rank him (under League then managers Rate!) And you may all decide to form a new league next year.
even if you are locked you can go to "managers" link and for those who have emails showing, get together next season w/o this commish. you also can't be locked out of the team trash talk line either so rant in there if you want. yahoo doesn't get involved in pvt leagues.