.....is very interesting. Unlike the Constitution, it is the actual moral content of the law, not the structure of the lawgiver and enforcer, that is the primary emphasis. That said, we can infer some things from what is said. For example, take a look at Deuteronomy 16:18-17:20. It is very interesting in what it does, and does not, do.
First of all, Moses introduces us to the requirement that the Israelites appoint judges and officers "in all their gates," that is in all of their towns. Notice that just like Genesis 9:6, Romans 13, and elsewhere, the primary concern with human government in this part of the Bible is that justice be administered correctly. It continues to note that the next prohibition after perverting justice is a prohibition against....sacred groves and pillars as used in idolatrous worship. How different from our day, when we tell jokes which presume that our lawyers are often the worst of people, confusing the bar of justice with the bar at which alcohol is served, to borrow one awful joke. In that day, they were to be similar in character to the priests.
Next, in Chapter 17, Moses begins by prohibiting blemished offerings and idolatry--another implicit comparison of injustice to idolatry--and then proceeds to note that a death sentence may only be handed down with two or three witnesses--who must take part in the execution. Notice as well that the priests and Levites were to get involved in difficult cases. A lot of this parallels church governance and discipline in the New Testament, though for obvious reasons (Rome as pagan) Romans 13 does not suggest that Rome use the apostles in judgment.
Most interesting to me are verses 14-20; the king was to be chosen long after Moses, and he was to be an Israelite himself, not a foreigner. Moreover, he was to write out a copy of the Torah for himself, and he is not to collect gold, women, or horses--especially horses from Egypt. At this point, kings used gold for two purposes; getting palaces and harems, and to wage war. Horses, in turn, were primarily used by kings for waging war. In other words, this passage is concerned with preventing the kings of Israel from engaging in the practices of empires like Egypt.
Going further, Deut. 19: 15-21 prescribes very harsh penalties for perjury, and Deut. 20 specifies certain practices and limitations on war--limitations that, if followed, would make the Israelite practice of war far more humane than that of her neighbors--or at least far less monstrous. In other words, not like the empires of Egypt, Assyria, Babylon, Persia, Rome, and Greece.
It is worth noting that in the Torah, as in the New Testament, the responsibility of charity falls on the people, and upon the church, not the government.
The summary here is that government was to be primarily concerned with justice, and that the kings were to cling to the law and avoid the practices of empire. If you're thinking about Solomon right now, so am I. We'll get around to him soon, Lord willing.
It's worth noting here, by the way, that groups who seek to pull our government away from practices of empire, and toward real justice, are on the right track--the question is not generally motivations, but whether they get it right.