In lightning chess matches (matches with time controls of 3 minutes or less on each side), some players play with the rule of "king sniping" - that is, to save time, if the opponent played a move that left his king in check, the other player can simply capture it (thereby winning the game) rather than forcing the opponent to retract his move.
Combined with the rule that the king cannot castle through check (cannot move two spaces if the space between the origin and destination is attacked by an opposing piece), the problem arises of what the appropriate way is to capture the king if this actually happens in a lightning match, as the king is not in a position of check either before or after the opponent's turn. Simply taking the king away might confuse the player because the other piece will have made a technically illegal move, but moving to the square that the king castled through (which amounts to a sort of "en passant" capture, capturing a piece/pawn that moved two squares in a special case as if it had only moved one square) captures the rook instead of the king.
Is there any convention for this?