If a rule requires a player who has left the game to make a choice, the next player in turn order makes that choice.
August 23, 2019 · Commander 2019
If an effect requires information about a specific player, the effect uses the current information about that player if they are still in the game; otherwise, the effect uses the last known information about that player before they left the game. If an effect requires information from the game about actions players have taken, the effect can find actions that were taken by a player who has left the game.
April 27, 2018 · Dominaria
If an effect requires information about a specific player, the effect uses the current information about that player if they are still in the game; otherwise, the effect uses the last known information about that player before they left the game.
June 5, 2017 · Commander Anthology
If an effect requires information about a specific player, the effect uses the current information about that player if he or she is still in the game; otherwise, the effect uses the last known information about that player before he or she left the game.
February 1, 2012 · Dark Ascension
If a player leaves the game during his or her turn, that turn continues to its completion without an active player. If the active player would receive priority, instead the next player in turn order receives priority, or the top object on the stack resolves, or the phase or step ends, whichever is appropriate.
September 30, 2011 · Innistrad
When a player leaves the game, objects that player owns in the ante zone do not leave the game. This is an exception to rule 800.4a. See rule 407, "Ante."
June 17, 2011 · Commander 2011
When a player leaves the game, objects that player owns in the ante zone do not leave the
April 1, 2011 · Duel Decks: Knights vs. Dragons
When a player leaves the game, objects that player owns in the ante zone do not leave the game. This is an exception to rule 800.4a. See rule 407, "Ante."
February 4, 2011 · Mirrodin Besieged
When a player leaves the game, objects that player owns in the ante zone do not leave the game. This is an exception to rule 800.4a. See rule 407, “Ante.”
October 1, 2010 · Scars of Mirrodin
When a player leaves the game, objects that player owns in the ante zone do not leave the
February 1, 2010 · Worldwake
When a player leaves the game, objects that player owns in the ante zone do not leave the game. This is an exception to rule 800.4a. See rule 407, "Ante."