In Round 15 of Pro Tour Ixalan, competitor Yao Zile was disqualified for using an improper method to determine the outcome of the match. The following is a statement from the tournament's head official:
"Yao Zile and his opponent, Luis Scott-Vargas, reached the end of extra turns in a match that would, if played to the end of that turn, result in an unintentional draw. Both players revealed their hands and discussed a possible outcome of who would win based on the available information at the end of that game.
At that point, Yao mentioned that he needed a specific card to win, so he revealed the top cards of his deck to see if it would influence the decision of whether or not to concede.
In tournament policy, a player can only use information that he has access to already through naturally playing a game of Magic to discuss possible outcomes of a match.
Yao, in arguing his case of his possibility to win, revealed cards from the top of his deck to discuss the outcome of a match. Because of this, the ruling was made that he used an improper method to determine the outcome of the match. The penalty resulted in a disqualification of him from the tournament."