I didn't see it as a role of the DU to monitor who accepts duel challenges and who doesn't among students.
It is the role of the Elders of the guild to maintain decorum and civility among their members.
I do try to maintain a separation between who you are in the "real" world and who you are in the University. This is a courtyard brawl between students that professors should not get embroiled in it to decide who is right and who isn't.
In a way, I agree. They should not step in and say determine who is the right and who the wrong. But they *should* step in and say "This behavior is unacceptable in the University." The Elders need to step in and stop the brawl, and make it clear that brawling isn't allowed.
But it is true that that's not very medieval: a Duke is a Duke, and should be treated as such everywhere.
I agree.