In saying that, Jesus was referring to something that the people were well - aware of, for according to the Mosaic Law, judges in the cities were appointed to rule on just such matters.
وَمَهْمَا كَانَ ٱلسَّبَبُ ٱلَّذِي دَفَعَ ٱلرَّجُلَ إِلَى تَقْدِيمِ هذَا ٱلطَّلَبِ ،‏ فَإِنَّ يَسُوعَ لَمْ يُلَبِّ طَلَبَهُ .‏