War has midwifed political theory since at least the time of the Ancient Greeks. John Rawls, the doyen of political liberalism, embarked on his grand theoretical quest after he came back from the Pacific theater, where he witnessed the aftermath of the Hiroshima bombing. Italian legal philosopher Bruno Leoni, who would have been 100 years old today, does not enjoy Rawls’s international renown. But Leoni, who died in 1967, wrote a book, “Freedom and the Law” (1961), that deserves a place in the canon of modern libertarianism. He was likewise deeply influenced by World War II, although in an unpredictable way.

As Hitler and Mussolini exited the stage of history, Leoni did not think the battle for freedom was won. He was a successful lawyer and academic, a vibrant polemicist for 24 Ore, Italy’s business daily, and an indefatigable cultural organizer.

And Leoni had had a “good war.” As liberty mattered more to him than blood, he fought with the Allies, leading dangerous missions to free British prisoners behind enemy lines. In the process he perfected his mastery of the English language and developed a distinctive appreciation of the British mind.

Leoni saw a basic difference in the understanding of freedom between the Anglo-Saxons, who never flirted with totalitarianism, and Continental Europeans. This, in his view, could be traced to the differences between the common-law tradition, on the one hand, and the Continent’s legislation-focused approach to the law.

Theorists of freedom have repeatedly argued that laws should be general, abstract, universally applicable and written down, so they could be knowable by the sovereign’s subjects. We are free when everybody is subject to the very same law. Certainly, as Leoni wrote, general rules — “written laws” — are “an improvement over the sudden orders and unpredictable decrees of tyrants.”

But parliaments and regulatory bodies all over the world produce written laws, which typically come out of meticulously followed procedures. Is that enough to give us freedom and legal certainty?

The formal procedures are upheld, but intrusions into private and economic life are frequent and clearly more pervasive than they were in the past. Legislative technique has improved and the number of scholars and practitioners of law has grown exponentially. But we do not necessarily enjoy more legal certainty than we did in the 18th or the 19th centuries. In many cases, the opposite is true.

Thinking of the nefarious regimes he fought against during the war, Leoni understood that legislation was in some ways analogous to central planning. Central planners design the production in an economy by directly allocating factors of production. Legislators attempt to plan economic life by changing the rules of the game so as to allow their champions to win economic competition. Central planning was discredited with the end of communism. But legislation, its more legally refined surrogate, is here to stay. Modern regulatory bodies enforce laws that may have been crafted according to perfectly well-defined procedures, but they aim at commanding economic resources.

The rule of law so conceived, then, is nothing but the rule of men under another name. One century before Leoni, the British philosopher Herbert Spencer wrote that “over-legislation” produces “officialism,” the rule of bureaucrats. Officialism, Spencer argued, is slow, unadaptive and extravagant — which is a fitting description for most of today’s governments.

Leoni pointed out that good law could be made — but, like any good product, its production could not be entrusted to central planners. The alternative to this top-down, centrally planned approach was English common law. It was not perfect, since law is a human artifact. However, judge-made law, crafted one precedent at a time, allowed for “a sort of vast, continuous, and chiefly spontaneous collaboration between the judges and the judged in order to discover what the people’s will is in a series of definitive instances — a collaboration that in many respects may be compared to that existing among all the participants in a free market.”

The difference between legislation and the old common law system was basically that the second built on a better learning process than the first.

Learning for legislators is difficult, as for them law-making is a process of building political consensus. Legislators make and remake law depending on the pressures coming out of their constituencies. And by doing so they transform law in a more malleable good than it should be. “Written” laws, Leoni argued, allowed only for “short-term legal certainty.” Witness the mad rush to “do something” in any national capital after a crisis, or a scandal, or some other public outcry. With each disturbance, legislators rush to write and rewrite laws, often without considering whether existing laws were broken, or whether they are adequate to punish those who may have broken the law.

The certainty of law, Leoni argued, only comes from a process that gives priority to the past over the present. The burden of proof is on the shoulders of reformers. New norms by their nature undermine confidence in the current set of rules. There should be therefore a real demand for them. But this demand should not transform immediately into new laws when a business or a consumer group “captures” the decision maker. Judge-made law ultimately filtered people’s never-ending demand for political action, in part because case-made law is restricted to dealing with actual cases and controversies, rather than possible or hypothetical ones. Law is still a balancing act: But it should not be balanced between legislators and special-interest groups.

This is what Bruno Leoni realized fighting against the legal government of his very country in World War II. For Leoni, liberty consists of keeping the lives of people and the resources they command out of the political sphere as much as possible. Law should filter, rather than facilitate, the tendency toward the full politicization of human life that was so apparent in the 20th century. Thinking of the never ending production of norms undertaken by the European Union, national parliaments and regulatory bodies, his lesson is perhaps more timely than ever.