Back home in the Bronx is where I first heard the old saw about the Irishman who, coming upon a donnybrook at the local pub, asks a bystander: “Is this a private fight or can anybody join?”I was a much younger fellow then. The prospect becomes less alluring with age, so I have some trepidation stepping in between two old friends, Andrew Napolitano and Joe DiGenova. Through intermediary hosts, the pair -- Napolitano a former New Jersey Superior Court jurist and law professor, DiGenova a former United States Attorney for the District of Columbia and prominent defense lawyer -- brawled this week on Fox News (where I, like they, contribute regularly).I’m going to steer clear of the pugnacious to-ing and fro-ing. Let’s consider the intriguing legal issue that ignited it.Judge Napolitano argues that the July 25 conversation between President Trump and Ukrainian President Volodymyr Zelensky contains the makings of a campaign-finance crime. He highlights Trump’s request for Ukraine’s help in i...