In 1 Samuel 8, Israel infamously demands that Samuel appoint for them a king. This event involves some weighty issues for the idea of law and authority. On the surface, at least in many popular readings, what happened may seem simple: God was Israel's only king, but they grew jealous of nations having tangible kings, so they wanted to replace God's authority with that of a king. This, however, misses a couple of important features of the situation. For one, it is too simple to suggest, as often happens, that God was meant to be Israel's only king. On the contrary, in Deuteronomy 17, God had already made provisions and permission for Israel to have a king. Moreover, the offense is not only against God. He says to Samuel that they are rejecting him like they had been rejecting God already all since they came out of Egypt.
These two qualifications highlight two useful points. First, divine and human authority is not a zero-sum game. God's decrees and wise human rule do not conflict at the level of principle. Already in God's law, the lesser agency of human wisdom and authority finds authorization. There was a way that Israel could have been ruled by a king without compromising their fidelity to divine authority, but whatever that route would have been, they did not take it.
Second and related, it is the reject, not the acceptance, of human authority that seems to follow rejection of divine authority. They rejected God first, then they rejected Samuel. They wanted a new authority of their own preference. This they willed despite all of the warnings of how he would mistreat them. In rejecting the authority God had already put in place for them, they willingly enslaved themselves to a crueler authority.
This last note catches a bit of the resonance of the Fall here. Adam and Eve were given a divine command prohibiting them, probably temporarily, from the tree of the knowledge of good and evil. This language is connected elsewhere in Scripture to royal wisdom, implying that they sought royal judgment before royal maturity to wield it. So they exchanged the divine law they had to serve another master, in this case willingly subjecting themselves to the Serpent in their "liberation" from God. Israel likewise, before she was truly at rest (as the provision in Deuteronomy seemed to require), urged for royalty too quickly, and she finds herself willingly subjected to the serpentine Saul.
There is an irony to this new slavery to the serpent-king in God's initial reference to delivering them from Egypt. Pharaoh was already a serpent figure enslaving the people, and this is from whom God redeemed them. Yet they have rejected the God who freed them and now willingly enter slavery again. This new king is described in a way reminiscent of Pharaoh, even! But this time around, "you will cry out because of your king, whom you have chosen for yourselves; but the Lord will not answer you in that day."
The tyranny God predicts from the new king highlights another matter pertinent to the matters of law and authority. Tyranny is bad, and the laws in Deuteronomy explicitly prohibit the kinds of behavior that Samuel prophesies here and in which Saul (and later kings) actually engages. So there is a fundamental wrongness to tyranny. The king is not quite the state alone, nor is he above the law, but he is accountable to God even when they are no other checks in place. This is relevant to questions of how far a ruler's authority truly goes when they become a tyrant, a limiting concern that is hard to hold up without the idea of divine judgment.
One final note: the king is representative of the people. They asked for him, they drink his health, they pay his taxes. They invite him to govern them and go out before them and fight their battles. These people know the Torah, presumably including the portions about the behavior of a king, but they are willing when warned to accept a king who breaks it. To request a Torah-breaking king is to assert themselves as a Torah-breaking people.