Historical Rules · 30 September 2011
Rule 111.2
Official source text from the 30 September 2011 Rules release
A spell's owner is the same as the owner of the card that represents it, unless it's a copy. In that case, the owner of the spell is the player under whose control it was put on the stack. A spell's controller is, by default, the player under whose control it was put on the stack. (For noncopy spells, that's the player who cast it.) Every spell has a controller.