Following the Gunpowder Plot, Blackwell wrote to Rome and obtained a letter from Pope Paul V condemning the plot and calling on English Catholics not to disturb the peace. Part of the English government's response was to enforce a new oath of allegiance, drafted in such a way that it was bound to create divisions within the English Catholic community as to whether it could be taken in good conscience. In particular, one passage of the oath could be read as giving the English authorities the right to define heresy.