§ 366.1 Core Rules PDF (officieel)

Passive Abilities of cards in zones that are outside of the Board will self-describe their context. Example: The passive ability "Play me only during an opponent's turn." applies in any zone from which that card can be played. Example: Undying Legion has a passive ability that reads “[Legion][>] You may play me from your trash for [3][C].” That passive ability only applies when Undying Legion is in the trash.