Rule 810.8a

Players win and lose the game only as a team, not as individuals. If either player on a team loses the game, the team loses the game. If either player on a team wins the game, the entire team wins the game. If an effect says that a player can’t win the game, that player’s team can’t win the game. If an effect says that a player can’t lose the game, that player’s team can’t lose the game. Example: In a Two-Headed Giant game, a player controls Transcendence, which reads, in part, “You don’t lose the game for having 0 or less life.” If that player’s team’s life total is 0 or less, that team doesn’t lose the game. Example: In a Two-Headed Giant game, a player attempts to draw a card while there are no cards in that player’s library. That player loses the game, so that player’s entire team loses the game. Example: In a Two-Headed Giant game, a player controls Platinum Angel, which reads, “You can’t lose the game and your opponents can’t win the game.” Neither that player nor their teammate can lose the game while Platinum Angel is on the battlefield, and neither player on the opposing team can win the game.