AboutTony D'Aloisio Expertise I've read a good deal on the subject and I can answer a lot of chess history questions (or at least I'll know where to look them up). Also questions regarding analyzing specific positions (although with the advent of powerful chess software, this isn't likely to have the importance it once did).
Experience I was a national master in the US for a number of years. My peak USCF rating was 2290, and I was ranked in the top 150 in the state of California. My current published rating is 2177.
Education/Credentials B.A. Sonoma State University 1984 (English major with Communications emphasis)
Question If a player makes an illegal move, such as moving a black squared bishop to a white square, has he/she forfeited their game, or are they allowed to take the move back and make a new move with the original bishop?
I ask this because I have read that illegal moves can be corrected when observed. But, if this is true and since we play without a clock (his preference) a player can make one illegal move after another, it, in fact, would encourage cheating which my opponent has admitted he will do if it helps him to win.
If it exists in printed form that such moves result in forfeiture please give me the source if you can.
thanks for considering this question.
pepe
Answer In general, they are allowed to take the move back. According to the rules of the International Chess Federation (FIDE):
"7.4 If during a game it is found that an illegal move has been made, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined the game shall continue from the last identifiable position prior to the irregularity."
You should bear in mind though that there are two substantial differences between off-hand, friendly games and official tournament games: 1) tournament games use clocks; and 2) both players keep a record of their moves (the "scoresheet"), which makes it much easier to reconstruct the position in question.
The only instance where one can lose under official rules by making an illegal move is in so-called "blitz" games (i.e., each player has five minutes to make all of his or her moves); if a player leaves their king in check without noticing it, the king can be captured by the opponent, thus ending the game immediately.
My advice, if you are concerned about the possibility of your opponent making illegal moves, would be to play him online, where the software will not allow such moves to be made.
