In the assigned readings from Jacob Lauterbach’s Rabbinic Essays, I notice the following passage from page 209:
In the opinion of these democratic lay teachers…the right to decide religious questions given in Deut. 17.9ff. to the priests was not given to them as a family privilege merely because they were priests, but because they were teachers of the Law, and only as long as they were teachers of the Law. The same right was equally granted to the teachers of the Law who were not priests.
I guess that’s how the Pharisees gained the right to interpret the Torah, in the eyes of many Jews. The Pharisees weren’t priests, but they claimed to be teachers of the Law. Although Deuteronomy 17:9 gives the priests the authority to decide in matters of the Law, Lauterbach’s point is that some felt that the priests were not necessarily faithful to the Torah (if I’m reading Lauterbach correctly).
Catholics have appealed to Deuteronomy 17:9 to argue that the Catholic church has the authority to decide in matters of faith and practice. Like the Pharisees, however, Protestants hold that the Bible does not equal the Catholic church’s interpretation and application of it, but rather stands independently of the church, over and above it. The Catholic church probably doesn’t support abusing its power, however, for it admits that the church has done wrong things in the past, implying that there is a standard of right and wrong that is above the church. Yet, I’ve also read Catholics who claim that, when the pope speaks ex cathedra, God keeps him from making an error.