
Originally Posted by
Igor_Goldenberg
It can be argued (to death) that position means placement of pieces on board that be achieved by the series of legal moves (or not).
Then it can argued (also to death) whether move that leads to an illegal position can be legal.
It could also be argued (again to death) whether "checkmate position" must be a legal position.
I'm sure you could argue to you are blue in the face however as far as I am aware, the position terms just refers to the placement of the pieces and does not imply a legal sequence of moves from the starting "position".
I note there is a definition of position (at least with respect to rule 9.2) given which goes...
Positions as in (a) and (b) are considered the same, if the same player has the move, pieces of the same kind and colour occupy the same squares, and the possible moves of all the pieces of both players are the same.
And I think the general convention is exactly this. The term "position" refers the sum of the location of all the pieces and all possible legal moves of the colour with the move.

Originally Posted by
Igor_Goldenberg
All in all it means:
1. An arbiter will have to make a decision (in case of dispute) using whatever interpretation (s)he thinks is correct. Not a good idea.
2. Proper wording has to be made by FIDE.
3. Obviously conflicting rules (checkmate ends the game and irregularity clause) have to be reconciled one way or another.
I would argue that an arbiter would just need to be conversant with the laws as they stand and the standard interpretation of them. Not all arbiters are of course.
You can also argue until you are blue in the face about the wording of any set of rules. Adding a clause to define position as the location of the pieces on the board and all possible legal moves for the colour with the move might be nice but as that is already in 9.2 it would seem to be not patently required.

Originally Posted by
Igor_Goldenberg
Questions:
1. Suppose white made an illegal move, black responded, white responded, black checkmated. How do you want the law of chess to treat the result?
2. White made an illegal move (leading to a legal position), black checkmated. How do you want the law of chess to treat the result?
How you, I or anyone else would like the laws of chess to treat the result is a little beside the point. The current laws are definite. Legal move ending in checkmate is checkmate and thus ends the game. The problem with looking back 2, 3, 4 or any other number of moves and ensuring all legal moves presents arbiting problems and so while I believe Geurt has wanted to change this law there has been considerable resistance to change.