Rule 801.5a

If a player is asked to choose an object or player, they must choose one within their range of influence. Example: In a game with a range of influence of 1, Alex is seated to the left of Rob. Alex activates the ability of Cuombajj Witches, which reads, “{T}: Cuombajj Witches deals 1 damage to any target and 1 damage to any target of an opponent’s choice,” targeting Rob and choosing Rob as the opponent who picks the other target. Rob must choose a target that’s in both his range of influence and in the range of influence of the controller of Cuombajj Witches. He must therefore choose himself, Alex, or a creature controlled by either himself or Alex.