For every dispute that comes before you from your brothers who dwell in their cities—whether it regards bloodshed or some other violation of law, commandments, statutes, or ordinances—you are to warn them, so that they will not incur guilt before the LORD and wrath will not come upon you and your brothers. Do this, and you will not incur guilt.
Jehoshaphat, having done what he could to make his people good, is here providing, if possible, to keep them so by the influence of a settled magistracy. He had sent preachers among them, to instruct them (Ch2 17:7-9), and that provision did well; but now he saw it further requisite to send judges among them, to see the laws put in execution, and to be a terror to evil-doers.
Commenting on 2 Chronicles 19:5-11
And, behold, Amariah the chief priest is over you in all matters of the Lord,.... He being high priest, presided in this court in all things sacred, or which respected the worship of God; and was present to give his advice, and direct in the determination of all such matters that should come before them, according to the laws and statutes provided in such cases...
And what cause soever shall come to you of your brethren that dwell in their cities, between blood and blood, between law and commandment, statutes and judgments, ye shall even warn them that they trespass not against the LORD, and [so] wrath come upon you, and upon your brethren: this do, and ye shall not trespass.