Jehoshaphat had previously sent teachers throughout the land of Judah to teach his people the ways of God. Now, you have surely heard it stated, people do not do what you expect, they do what you inspect. Jehoshaphat was wise enough to do some inspecting. Even though he had made a serious mistake in making a league with Ahab (and, yes, he got into trouble for that), he didn't allow that to stop him from holding his people accountable for the truth which they had been exposed to.
It should go without saying that information alone is not necessarily beneficial. Even good spiritual truth (though it is packed with potential and power) must be unpackaged and implemented to be productive and fruitful. Jehoshaphat expected his people to react appropriately to the teaching which they had received. So, he sent judges throughout his kingdom to make sure that they did indeed allow the truth to set them free.
Now, concerning those judges, Jehoshaphat charged them to make their judicial decisions and to issue their edicts based upon God's shadow as it was cast over them, not considering the contrary preferences of any man or group of men (2nd Chronicles 19:6). Additionally, Jehoshaphat specifically called those judges to consider God's transcendent perfection as the ultimate Judge (2nd Chronicles 19:7). He was inferring plainly that they should never play favorites, nor accept bribes.