So I have the magistrate's cudgel equipped on Eder, and the initial ability on it is
"Judge: Marked for 30.0 sec on scoring Hit, +10 Accuracy against targets affected by Judged effects."
this works the first hit after equipping it or switching weapon sets in combat, after that the debuff no longer gets applied to enemies, I've had Eder enter combat by himself to try this. You can earn the first level still by switching his weapon sets around until it unlocks but after that it still doesn't apply the effect. I'm unsure if there is an ability overwriting it or anything or if its unique to only Eder, I wouldn't know since I haven't bound it to anyone else.
I should note that this is my second play through and I've only experienced this bug running the Beta Patch 73. My original game didn't have this problem in the regular release client. I'll upload my latest save.
https://www.dropbox.com/s/wvp78kvfbv2o95j/Bug%20Report%20Magistrates%20Cudgel.zip?dl=0