If a Game Effect prevents the performance of a game action, that effect doesn’t prevent cards and abilities that instruct a player to perform that game action from being played or finalized. On resolution, that game action will be skipped as it is an impossible instruction. Example: A player plays Here to Help when their opponent controls a Mageseeker Warden at a battlefield. Here to Help is legal to play under these circumstances. On resolution, no unit will be played.
§ 358.3.a Core Rules PDF (officieel)
§ 358 5. Check legality.
§ 358.3 Check that the outcome of the effect of this card being played would not create an illegal state. Example: Check that a spell's execution does not create a state where a Battlefield has Units controlled by 3 different players.
