Question: I was playing with someone who refused to play after the Charleston because she didn’t like her tiles. Is this allowed?

Answer: Once the mandatory first and second Charleston moves have been completed the game must be played even if a player dislikes the tiles they have. Throwing one’s tiles in to request a do-over is not allowed and a sign of poor sportsmanship.  This ruling is not found in Mah Jongg Made Easy.

Source:  National Mah Jongg League Bulletin Q&A (1994 page 5)