Historical Rules · 15 February 2021
Rule 303.4i
Official source text from the 15 February 2021 Rules release
If an effect attempts to put an Aura onto the battlefield attached to an object or player it can’t legally enchant, the Aura remains in its current zone, unless that zone is the stack. In that case, the Aura is put into its owner’s graveyard instead of entering the battlefield. If the Aura is a token, it isn’t created.