In the late 13th century a new person came to hold the office of pope. Boniface VIII became pope after Celestine V, who resigned his office as pope because he was being taken advantage of by the cardinals and monarchs. Right away Boniface had enemys since Celestine had supporters from the spiritual Franciscans who believed in a prophecy that Celestine would usher in the age of the Holy Spirit. At this time Phillip the fair of France(also known as Phillip the IV) decided to tax the clergy of France to pay for his wars with England. This was against the rule that the king had to ask the pope before he could tax the clergy. Boniface responded by telling the clergy of France to not pay the tax. In response the king forbade any of the churches revenue from going to Rome. After this Boniface changed his mind since the pope needed the revenue to operate. Not long after this skirmish Phillip the fair imprisoned a bishop in France and refused to let him be tried in the churches court. Boniface VIII then sent a letter to the king of France telling him that he should leave these things up to the pope. Instead, before the letter reached Phillip, his courtiers doctored the letter to basically say that the pope claimed that he could be the king of France. To counter this Phillip sent soldiers to the pope to rough him up. This so shocked the pope that he died several weeks later. This was evidence that the power of the pope was beginning to wane.
In the early 14th century there was a political thinker named Marsilius of Padua. He wrote a book called Defensor Pacis (Defender of Peace) in which he stated that the state should be autonomous and the church should have no control over it at all. The pope would be reduced to an honorary role and the only power he would have would be to declare what the ecumenical councils decided, but the state would have control over that as well. The kingdoms law would be sovereign and only if the law was extremely against Christian law could you disobey the states law. But this was by far the exception and he vouched for the states complete control in everything else. Law would also just be a thing that the state forced you to obey and there was no eternal law that transcended the kingdoms control. This was the beginning of more modern thinking.