Classic chess rules

Illegal move

A player who makes an illegal move must retract that move and make a legal move. That move must be made with the same piece if possible, because the touch-move rule applies. If the illegal move was an attempt to castle, the touch-move rule apples to the king but not to the rook. If the mistake is only noticed later on, the game should be restarted from the position in which the error occurred.

If blitz chess is being played (where both players have a limited time, e.g. five minutes) the rule varies. A player may correct an illegal move if he has not pressed his clock. If he has pressed his clock, the standard USCF rule is that two minutes are added to the offender's opponent's clock. An alternative USCF rule is that the opponent can claim a win by forfeit if he has not touched a piece. If the player has left his king in check, the opponent may touch his piece that is giving check, remove the opponent's king, and claim a win (Just & Burg 2003:291–92).