Disqualified Player Must Remain Silent (Article ID 34)
Abstract: If a player has been declared dead and notices another player’s hand is dead, they cannot call that player’s hand dead. Any player whose hand has been declared dead must remain silent during the remaining part of the game.
Question from a player: If a player has been declared dead by another player and is no longer playing, but notices that another player has a dead hand, can that dead player declare the other player dead, or is she considered no longer part of the game?
Answer from the NMJL: A player whose hand has been declared “dead” must remain silent for the remainder of that hand.
Source: Mah Jongg Made Easy (2020 page 31 para. 5)