The GM as safety net

[Sven Seeland]

I think that you can also design a mechanic to allow players to challenge a player that that they feel has gone too far, if you feel this is a concern for a game you are creating. This perhaps could help to ease some of the tension of a nonscripted freeform challenge, especially amongst people whom may not know each other, or each others comfort areas.

Actually, a few games have already done this very successfully. Some that come to mind are Universalis (which is GM-less), The Verge (which is still under development, but already pretty exiting) and, as far as I know, Capes, which is written by ours truely TonyLB. I could be mixing up some things with Capes though...
Especially Universalis shines, in my oppinion. The use of tokens and bidding to get certain facts into and out of the game is pretty brilliant, in my mind.

[GB Steve]

In many narrative-based games, I would like to give the GM the power to edit whatever the players narrate. That is, he can say no to something the players narrate...

As a GM this is something that I do a lot, particularly in the character creation stage, which in the more traditional games that we play is the area of the greatest player freedom.

Part of our usual set up is that one of the players will have to go through an exploration process until he can "get" (or "grok" for you old hippies) the game. This usually involves making several characters and seeing how they interact with the rules and to a certain extent me saying why what's he's attempting to do does or doesn't fit in with the other characters, the theme (or premise even) of the game or the game world as presented in the background. After we get through that process, he's a great player to have around, very inventive. On the other hand he can easily completely derail convention games and can be seen as antagonistic although I see it more as a learning style (and possibly linked to his severe dyslexia).

Our group now explicitly recognises this as part of the social contract, although not always happily.

Polaris, which for Graham's sake, share out the traditional GMing responsibilities between the players has mechanisms for conflict resolution which basically amount to the same as Dogs (with which Graham is familiar). The GM does it in Dogs but in Polaris, the players agree with whatever is proposed for their area of responsibility and when they don't there are methods of conflict resolution.