  The classical work in deontic logic that was begun by von Wright (see  von Wright 1983)  is one source of ideas; see  (Horty 2001,  van der Torre 1997).  In fact, as the more recent work in deontic logic shows, nonmonotonic logic provides a natural and useful supplement to the classical deontic logic.  One recent work (Horty 2012) seeks  to base deontic logic on a prioritized version of Reiter’s default logic. 