355.2. Ensure 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.
355.3. If the card, if continued to be played, would create an illegal state, or if a choice or action at this state is illegal, the actions taken in this process are undone and the action is cancelled.