Commitment to a Joker Exchange (Article ID 19)
Abstract: Once a player receives a joker after it is replaced with the same symbol tile, the exchange cannot be reversed. They have committed to the exchange. This ruling is not found in Mah Jongg Made Easy.
Question from a player: When it is a player’s turn, they made an exchange of a joker by taking the joker and replacing it with the same symbol tile. Before they place the joker in their rack, they change their mind and want to put the joker back. Can they do so?
Answer from the NMJL: “Once you make an exchange, you have already made your play and made a commitment.”
Sources: National Mah Jongg League Bulletin Q&A (2001, 2014, 2015) https://www.nationalmahjonggleague.org