If the Pope, being neglectful of his own salvation and that of his brethren, be found useless and remiss in his works, and, more than that, reluctant to do good (which harms himself and others even more), and nonetheless brings down with him innumerable throngs of people … Let no mortal man presume to rebuke him for his faults, for, it being incumbent upon him to judge all, he should be judged by no one, unless he is suddenly caught deviating from the faith…

– Decretum Gratiani, Si Papa, dist 40, ch 6 (attributed to Saint Boniface)