Actually, Alecto, the fact that each city has a ministry of Justice is purely a coincedence. Certainly, certain cities might choose to adopt justice or not. There is no 'must' in the matter.
In fact, from a historical perspective, Thakria has always had a neutral (at best) attitude towards the god of Justice. Mercinae had very strong ties in that direction though.
Keen fans of history might also remember that spiting the god of Justice was a very important goal of the first invasion of Mercinae. Of course, much has changed since then, and Thakria does indeed seem to have a strong justice motif going currently.
In closing, no city must abide by any realm. Mortals can, and should forge their own paths, and Thakria has least reason to have anything to do with justice.
Written by my hand on the 13th of Paglost, in the year 1016.