108.3b

Some spells and abilities allow a player to take cards they own from outside the game and bring them into the game. (See rule 400.10b.) If a card outside that game is involved in a Magic game, its owner is determined as described in rule 108.3. If a card outside that game is in the sideboard of a Magic game (see rule 100.4), its owner is considered to be the player who started the game with it in their sideboard. In all other cases, the owner of a card outside the game is its legal owner.

Burning Wish.