In solo mode, could Augustus "Guard" twice per turn?

On Augustus' COG card, it states that "even another player" has played a Guard card, and there is no official rules that modify his ability in solo play. So I would say he cannot "Guard" twice in a turn, and his ability essentially becomes only "play any card as a 'Guard' card" in solo play.

Nevertheless, it is your game so play it however you like.

Thanks for the answer Angus!