This came up at our table the other day...

"But what if the player does [something stupid]."

Then he sucks as a player and should be told as much. We're adults. If someone is ruining the game, you tell him so and we talk it out.

If he's doing it on purpose, he's a jerk and you can kill him and take his stuff.

If it's a matter of playstyle, well, that's we've been struggling with. But I believe everyone can get on board.

I guess there's an implied further question here: "Who has the right to call the player out on his bullshit?"

Well, everyone and no one. Depends on the game and, again, the group's social contract. Maybe we put all the power in one person's hands. But then that person also has all the responsibility. If he screws up, he screws up big time. Maybe it's an all around the table thing (and probably should be, most of the time).

Game systems are, amongst other things, about negotiating assent. Who has the right to say what, and who can deny him? The game should tell you. If it doesn't or it's unclear on that, fuck that game.

In D&D, the DM has the right to call for Ability Checks. But if you pay close attention, what's actually going on is a sort of group-assent. Of course the DM has the final call (because the rules say so) but I've seen it happen many times over that it was another player who called someone out.
"You can't just do that."
It happens less often with the DM but it happens
Player: "I/S/He should be able to do that easily!"
DM: "Ok, no roll." (or more commonly "Ok, I'll give you an easy DC.")

The game Archipelago boils down these social procedures into a set of rules. There is no GM, each player is responsible for a) their own character and b) an element of the setting (say, weather). You just narrate freely. But then, at any given time, anyone has the right to say "I don't think it's going to be that easy..." which means an action will have to be resolved by drawing a card. Everyone can also say "Try that another way..." when a player says something that you don't like. Plus a couple of other things.

I think that these "ritual phrases" that Archipelago uses could be theoretically bolted on almost any game out there, to strengthen group consent.