Bang! Calamity Janet and the High Noon Expansion
According to the creator of Bang! (Emiliano Sciarra) on BoardGameGeek:


  Actually, during the Sermon you cannot use Bang! cards during your turn only: it is allowed to use Bang! cards outside your turn. It follows that if you play a Duel, your opponent may answer with his Bang! while you can not, and so you will lose the Duel!
  As regards Calamity Janet, the general rule of thumb is that her Missed! cards are considered as if they were Bang! cards, so during the Sermon she cannot use Missed! cards as Bang! cards.