The focus of Sefer Devarim is perhaps the manner in which Moses reminds the people of Israel that the covenant made at Mount Sinai was not just meant for a people wandering through the wilderness – it was intended as a blueprint for the life of the Jewish people in their own land.
Commentators have pointed out that there are three basically different types of government. The first is dictatorship where one man rules without in any way consulting the people who are governed and the second is oligarchy where power is shared between a few powerful groups. The third is government based on covenant or constitution, which is the word we now prefer. A covenant sets out (usually but not necessarily in writing) the rights and obligations of the governed, the duties and limitations in the power of the rulers, the system of government, and the way in which disputes are to be adjudicated and criminals judged.
Whenever I read Parashat Shoftim I am always amazed to see how the Torah more than three thousand years ago required that the kings of Israel should not be omnipotent monarchs, that their authority was to be limited to avoid excesses and how the Cohanim [Priests] were prohibited from owning land to avoid corruption. The non-Jewish world discovered the virtues of the separation of powers in the 18th century (Montesquieu) and the dangers of corruption in the 19th century (Lord Acton). I have never heard even a vaguely satisfactory secular explanation as to how a group of ex-slaves wandering though the wilderness could have come up with such amazing political insights.
But what has all this to do with Yom Kippur?