When an event the Replacement Effect could apply to occurs, the player who controls the Replacement Effect may choose to apply it to the event.
§ 371.2.a Core Rules PDF (officieel)
§ 371 Some Replacement Effects will begin with “once each turn,” or “N times each turn.”
§ 371.2 If the Replacement Effect says a player “may” apply the Replacement Effect, the player has the choice of whether or not to apply it.
