What if the Cardinal Secretary of State, on visit to your country, voiced an opinion about a controversial draft law proposed by the president and on its way through the legislature? What if the draft law dealt with extremely difficult issues like where to draw the line between religious liberty and public duty, and risked upsetting a delicate balance, painstakingly struck over more than a century, over the role of religion in public life?

For French citizens, it’s not a hypothetical. Over the weekend, the Vatican’s Secretary of State, Cardinal Pietro Parolin, did just that. It might not quite be what the English call “not the done thing,” but it isn’t a thing that is done frequently or lightly. The Holy See is a sovereign actor -- one that guards its own internal affairs jealously -- and while popes are not always reluctant to use their position as a global bully pulpit, it isn't every day that the Vatican's senior diplomat weighs in on a major legislative question while it is a live issue.