Jamieson, Fausset and Brown on Deuteronomy 16:18-20

18-20. Judges and officers shalt thou make--These last meant heralds or bailiffs, employed in executing the sentence of their superiors.

in all thy gates--The gate was the place of public resort among the Israelites and other Eastern people, where business was transacted and causes decided. The Ottoman Porte derived its name from the administration of justice at its gates.