212.4e.

An Aura spell requires a target, which is restricted by its enchant ability. Other restrictions can limit what a permanent can be enchanted by. If an Aura is coming into play by any other means than being played and the effect putting it into play doesn't specify what it will enchant, the player putting it into play chooses a permanent for it to enchant as it comes into play. The player must choose a legal permanent according to the Aura's enchant ability. If an Aura is coming into play from the stack and there is no legal permanent for it to enchant, the Aura is put into its owner's graveyard instead of coming into play. If an Aura is coming into play from any zone other than the stack and there is no legal permanent for it to enchant, the Aura remains in the zone from which it attempted to move instead of coming into play. The same rule applies to moving an Aura from one permanent to another: The permanent to which the Aura is to be moved must be able to be enchanted by it. If it can't, the Aura doesn't move.