Originally posted by greenpawn34
Teacher has it right as far as I can see.
As soon as the game is over the result stands.
It should be added that touch move still stands.
If a player makes an illegal move with a Knight and it is spotted then
he must (if he can) make a move with that Knight.
Often wondered what would happen (and I'm sure it has).
A player makes an illegal ...[text shortened]... iegal move had not been played then the game would not have ended.
Messy grey area that one.
In your example: If White delivers a mate Re8# it isn't a mate only because it seems like a mate. Black can give up the game (as he can whenever he feels like it) and because of that, the game has ended as an agreed and confirmed win for white and lost for black. In that very moment the game has ended, and the result is fixed, and nothing more can be done about it.
The end of this game can be done in a chain of three actions. (1) The verbal aknowledgement ("Mate!" "Yes, it's mate, congrats!"
, (2) a handshake, and (3) a signature on the protocoll, ever one of these diging the hole deeper fror black. If he mumbles in (1) then he can claim that, "No, I didn't agree to anything, it's not mate because it was an illegal move!" Witnesses would be an help for the arbiter. Then handshake is visual and is not eaily missed by the witnesses. The signature confirmation is the strongest aknowledgement.
But when the game is over, it's over.
(I was once an arbiter in a tournament, when in the analysis after the game, they discovered that the black queen originally stood on e8 instead of d8. (yes it was a lower class tournament.) I asked the participants "Did you agere on the mate?" and both of the players said "Yes", so it was not much to discuss here.)
When shorter thinking times, like 30 min each or something, other rules aplies.