Amid the media frenzy over the morality play unfolding in an Ottawa courtroom, the bar has a lesson to glean from the argument over the interaction between the Canadian Senate’s expense rules and the Criminal Code.  (“Blame the rules, not Mike Duffy, defence says“; “Mike Duffy trial: Defence to continue attack on vagueness of Senate rules.”) Mr. Duffy’s defence lawyer contends the Senate’s self-imposed rules permitted practices such as claiming housing expenses for property in the province of a senator’s appointment, even though the senator resided in another province most of the time.  The Crown argues strict observance of this expense rule, to satisfy a questionable…