joshi tm: Certainly this problem needs to be fixed, and having an arbitrator would be one way to fix it, assuming that someone can be found who has the knowledge and the time and wants the job.

But there is a very simple solution that doesn't require any human intervention (except for a one-time bit of coding on Fencer's part). The rules of the American Go Association specify that when both players pass, fail to agree on the status of stones, and both pass again without placing more stones, the game ends immediately and all stones on the board are counted as alive. I can't think of any reason why something similar shouldn't be implemented here.