Historical Rules · 23 January 2015
Rule 712.5b
Official source text from the 23 January 2015 Rules release
The controller of another player can’t make choices or decisions for that player that aren’t called for by the rules or by any objects. The controller also can’t make any choices or decisions for the player that would be called for by the tournament rules. Example: The player who’s being controlled still chooses whether he or she leaves to visit the restroom, trades a card to someone else, agrees to an intentional draw, or calls a judge about an error or infraction.