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.)

704.5q If a creature is attached to an object or player, it becomes unattached and remains on the battlefield. Similarly, if a permanent that’s neither an Aura, an Equipment, nor a Fortification is attached to an object or player, it becomes unattached and remains on the battlefield.

So, is the rule 303.4d wrong, or do I miss something here?

Hi,

Those rules are covering different situations.

303.4d is discussing a situation where an aura becomes a creature, but still has the aura subtype. After it becomes a creature, 704.5q causes the aura to unattach, since a creature can't be attached to anything, then 704.5n sees an aura that's not attached to anything, and it goes to the graveyard.

The bolded section of 704.5q is talking about a situation where a creature is attached to a permanent, but does not have the aura subtype. In that case, 704.5q causes it to become unattached, and nothing further happens.

Nathan Long
Magic Rules NetRep