Natural law was what made the sentences in the Nuremberg trials possible, because, in accordance with the laws in force in their country, the architects of the Holocaust had not done anything illegal. As more than one said, also in the trials that followed Nuremberg, they only did "what they were told to do." "For a soldier, an order is an order," said Wilhelm Keitel.
That didn't save the former German field marshal from being hanged in 1946. Why? Because there is something that is above what a parliament or government can decide, of positive law, which is natural law.
Plato (c. 427-347 BC) or Aristotle (384-322 BC) already spoke about it, and it was at the root of the determinism of the Stoics, one of the main Greek philosophical schools. Centuries later, Dante Alighieri (c. 1265-1321) would write that any positive law that does not come from that primary source of legitimacy is immoral. From Saint Augustine (354-430) to the Enlightenment of the 18th century, finally, through the humanists of the Renaissance, all those who ever theorized about how a society should be organized recovered this idea.
Almost always, an obligatory appointment was Marco Tulio Cicero (106-43 BC), who, due to his rhetorical genius, was one of those who best defined the concept. In addition, circumstances forced him to talk a lot about it. Situated in the Cainite politics of the last years of the Roman Republic, he tried to refound it based on just laws. In his opinion, there is a tyranny just as bad as that of the satrap, which is that of the majority.
It was time to do political theory, since the old Italian democracy was devouring itself and its end seemed near. The confrontation between the optimates, the old senatorial aristocracy, and the populares, who represented the new citizens, was bitter. A struggle between conservatism and reformism that was sometimes resolved by violent clashes in the street, upsetting the outcome of the elections.
There were accusations of corruption against senators who, after an electoral campaign, accessed the government of a province only to plunder it and thus recover the money invested in buying votes. If we add to this the military reform of the consul Cayo Mario (c. 158-86 BC), which in practice made the soldiery more loyal to its general than to the State itself, all the ingredients were present for it to become imposed the new "strong men".
First there was the dictatorship of Sulla (138-78 BC), and then came Julius Caesar (100-44 BC), who said he would cross the Rubicon to save the Republic, but ended up giving it the last straw.
As a traditionalist republican, Cicero wrote tirelessly about the system he tried in vain to save, until Caesar's heirs lopped off his head. He did so in De republica and De legibus, two works in which he proposed a mixed constitution that would take only the best of the monarchy, the aristocracy and democracy. Ideally, it was about avoiding tyranny, oligarchy and ochlocracy, which would be the antagonists of each of them.
However interesting this may be, especially the concept of ochlocracy, which would be the government of a brutalized people, with a flawed will, what is central in this case is not the political thought of Cicero, which today could hardly be considered democratic, but the fact that it was based on natural law.
Like Plato, who said that "happy is the nation where philosophers are kings and where kings are philosophers", he thought that metaphysics was useless if it remained in a mere contemplative attitude, as the Epicureans understood it. For him, the search for the ultimate truth had to be useful, it had to be applicable to civil life and the government of the people.
He navigated through Platonism, Stoicism, Aristotelianism... and in the end he stayed with what he considered best of each one. That is why historians say that he was eclectic, because he wanted to reconcile the doctrines that made the most sense in the eyes of reason.
How to choose those doctrines? Necessarily, they had to be the ones that best adapted to the idea of natural law, which is innate to us. The latter defined it, in the style of a Stoic, as what is "according to nature."
This, and nothing else, was to be the measure of all things; especially in politics, which, being a practical philosopher, was always his field. In De republica he expressed it this way: “Neither the Senate nor the people can free us from obedience to this law. It does not need a new interpreter or a new organ: it is not different in Rome than in Athens, nor different tomorrow from today.
Where did that law emanate from? For Cicero, of divinity, and so thought most of those who followed him. Thomas Aquinas (c. 1224-1274) or Jaime Balmes (1810-1848), whom we could count among his disciples, understood that human morality is nothing more than an attempt to imitate God's perfect morality.
How this was translated into his political theory is something easy to explain, since it is like a varnish that permeates everything. His defense of justice, the rule of law, charity, respect for public and private property, compliance with contracts and the given word... all emanate from natural law. We can see it through his words.
