Quintilian, and J.S. Watson. Institutes of Oratory. Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book 7 Chapter 5.
When a defendant cannot deny responsibility for a crime Quintilian suggests it may be possible to demonstrate that the action against him is not legal (Quintilian VII.5.1). It is possible that the law does not allow the prosecution to proceed (Quintilian VII.5.2). The question of intention is also important (Quintilian VII.5.4). For instance, someone may commit a crime while saving his country from a threat. The actual wording of the law or contract is very important and must be examined closely (Quintilian VII.5.5).