Rule 303.4d

An Aura can’t enchant itself. If this occurs somehow, the Aura is put into its owner’s graveyard. An Aura that’s also a creature can’t enchant anything. If this occurs somehow, the Aura becomes unattached, then is put into its owner’s graveyard. (These are state-based actions. See rule 704.) An Aura can’t enchant more than one object or player. If a spell or ability would cause an Aura to become attached to more than one object or player, the Aura’s controller chooses which object or player it becomes attached to.