Historical Rules · 4 October 2019
Rule 702.16k
Official source text from the 4 October 2019 Rules release
“Protection from [a player]” is a variant of the protection ability. A permanent with protection from a specific player has protection from each object the player controls and protection from each object the player owns not controlled by another player, regardless of that object’s characteristic values. Such a permanent can’t be targeted by spells or abilities the player controls, enchanted by Auras the player controls, equipped by Equipment the player controls, fortified by Fortifications the player controls, or blocked by creatures the player controls, and all damage that would be dealt to it by sources controlled by the player or owned by the player but not controlled by another player is prevented.