In the absence of the checkmate rule, a chess game would be won by taking the opponent's king. Even if the winner's King were exposed to attack by the winning move, the winning move would ends the game and the loser cannot move to attack the winner's exposed King. Thus it would be permissible for the winner to expose the King on the winning move in a checkmateless game. In a game with checkmate, this translates into not allowing the King to expose himself to attack by an opponent's piece pinned to his King, since that pinned piece would ostensibly be able to take the King anyway, despite the created threat to the winner's King, since the loser would not be able to exploit the exposure, having lost. On the other hand, I think there should be another slight modification to the rules of chess that I think is consistent. The "en passant" rule says that if A's pawn moves two sqaures from the home rank, attacking B's pawn, and on the next play, B moves the attacked pawn one square forward to avoid capture, that A, on the next move, can capture B's pawn in the same rank as if A's pawn had moved only one square on the earlier move. But that same logic would apply to any piece that moved next to A's pawn in the same rank on the move following the A's two-square move. I argue that it should be possible to capture any piece en passant.