Any Christian leader who manages to separate mercy from rules in such a way as to prioritize the former over the latter would not really be merciful at all. Rather, he would be seriously delinquent in his duty. He might even be merely pandering to the spirit of this age.
Announcing the death of Benedict XVI on its Saturday front page, the New York Times drew a contrast between his papacy and that of his successor:
The two men were reportedly on good terms personally, but it was at times an awkward arrangement, and Francis moved decisively to reshape the papacy, firing or demoting many of Benedict’s traditionalist appointees and elevating the virtue of mercy over rules that Benedict had spent decades refining and enforcing.
As a Protestant and (at best) an amateur observer of things Catholic, I cannot comment on the fairness of this analysis. What is interesting, however, is the way the language, in its contrast of mercy with rules, points to deeper issues within society as a whole, Catholic and Protestant, religious and secular. In fact, mercy is incoherent if there are no rules, rules that are rightly believed and applied. Only if there is a rule, and a just rule, can forgiveness for its transgression be seen as an act of mercy.
More pointedly for Christianity, underlying the comment is the notion that rules can neither be motivated by nor embody mercy in themselves. This is a common but dangerous idea that, if true, would prove lethal to the faith. It is also rather selectively applied today. Christianity makes it clear that human beings are designed to be a certain kind of creature. We are free and self-determining in a way that other creatures are not: The swallow instinctively builds a nest but we design houses freely and intentionally. Our freedom, however, operates within certain parameters as set by the limits of human nature. I cannot jump off the Empire State Building and fly, for example, or dive into a cauldron of boiling oil and expect to emerge unscathed.