Albert Barnes Commentary 2 Chronicles 19:5

"And he set judges in the land throughout all the fortified cities of Judah, city by city," — 2 Chronicles 19:5 (ASV)

It is impossible to determine the exact change Jehoshaphat made to the judicial system of Judah (Deuteronomy 16:18; 1 Chronicles 23:4). He probably found that corruption was widespread (2 Chronicles 19:7) and that the magistrates in some places were tainted by the prevailing idolatry.

Therefore, he made a new appointment of judges throughout the entire country, either by concentrating judicial authority in the hands of a few or by creating superior courts in the chief towns (“fenced cities”), with a right of appeal to these courts from the local village judges.