Barring the Gates
Card abilities cannot cause characters to enter play.
While Barring the Gates is revealed, can card abilities (e.g. new Marge) bring duplicates into play?
I know Marshaling Orders prevents you from marshaling duplicates of attachments and locations, because you cannot initiate the marshaling action in the first place. Same with duping the Arbor.
However, the wording on Barring the Gates is kinda ambiguous. First, it does not directly prevent you from performing any game actions. Second, it refers specifically to characters entering play, not being put into play (which I think might be a bit different, like "means vs. ends"). Maybe the plot doesn't prevent players from performing certain game actions, but rather prevents abilities from resolving in a certain way.
As a very specific example, if I have a Night's Watch attachment or location in hand, can I trigger Old Bear Mormont to put his dupe into play? Whether you announce the card that you're going to put into play in Step 1 or Step 6 might be important here (I'm thinking of Scavenge in Netrunner).