By Allen R. Ferguson, Jr., JD, MFA

[Talk delivered to University of New Mexico Law School Faculty, Fall, 2005.]

The term “natural law” engenders a vague sense of uneasiness in many international lawyers and policy makers today, and a sharp sense of disdain in others. Perhaps the main reason for this is the historic association of natural law with Christianity. But the concept itself, as I intend to show, is not tied to any particular religion, or even to organized religion in general. This becomes clear when we recognize that many natural law principles pre-date Christianity, are common to a variety of religious and non-religious traditions, and can be understood outside of any religious framework.

My thesis today is that, despite the rejection of natural law by legal positivists and international lawyers over the past few centuries, natural law principles not only were central to the development of the modern international law of war and peace, but they remain central to that body of law today.

First, what do we mean by “natural law?” A simple dictionary definition seems most useful: Natural law is “a principle or body of laws considered as derived from nature [or] . . . reason . . . and considered ethically binding in human society.” At least this gives us a starting point.

What role did natural law play in the historical development of the international law of war and peace? Ancient and medieval philosophers and statesmen from China, to Greece and Rome, to the Middle East based much of their thinking about war and peace on principles that fit within the definition I have just given of natural law.

The Koran, for example, presaging the United Nations Charter and the Final Judgment at Nuremberg by more than a millennium, forbids aggression or the initiation of war: “Fight in the way of God against those who fight against you, but begin not hostilities. Lo! God loveth not aggressors.” The Koran also teaches the principle of proportionality, which we find in international law today. “If anyone attacks you, attack him as he attacked you.”

We see currents of thought that closely resemble modern international law principles even Centuries earlier, long before the appearance of Christianity. For example, in the Fourth Century B.C., the Chinese philosopher and military strategist, Sun Tzu, in his still influential book The Art of War wrote, “Ultimate excellence lies . . . in defeating the enemy without ever fighting.” Around the same time, half way around the world, the ancient Greek historian Thucydides wrote, “Not those who ward off force with force break the peace, but those who are the first to make the attack.”

The First Century A.D. Roman statesman and philosopher, Seneca, expressly drew on natural law for a principle in which we can see commonality with the modern prohibition against torture: “Although all things are permissible against a slave, yet there is something [that] the common law of living things forbids . . . against a human being.” Note Seneca’s expression, “the common law of living things.” I think we can agree that this is an expression of a natural law concept. The question is, does it have any reality? Is there a common law of living things?

Seneca also found in the natural laws that govern the human body guidance for the body politic. “Just as the members of the body agree with one another, because preservation of each conduces to the welfare of the whole, so men refrain from injuring one another [for] we are born for community of life. For society can exist in safety only through the mutual love and protection of the parts of which it is composed.”

Presaging Article 51 of the Charter, Cicero, the First Century B.C. Roman orator, wrote, “there is this law which is not written, but born with us; which we have not learned, . . . but . . . have sucked in. . . – the law that if our life has been placed in jeopardy by any snare, or violence, or weapons . . .every possible means of securing safety is morally right.”

Centuries earlier, Aristotle had drawn on nature to find guidance for human society with respect to peace and war.  Citing Aristotle, Hugo Grotius, the Dutch lawyer widely regarded as the father of international law, wrote in 1625, “Those nations which made warlike pursuits their end and aim” must be condemned for “violence is characteristic of wild beasts, and violence is most manifest in war; wherefore the more diligently effort should be put forth that it be tempered with humanity, lest by imitating wild beasts too much we forget to be human.”

Stating a fundamental principle that remains relevant to international law today, Polybius wrote, “Even when fighting evil ones, it becomes a good man not to involve the innocent in the same punishment as the guilty, but even to spare those who are guilty for the sake of the innocent.”

The passages from Greek and Roman writers that I have just cited are much more significant in the development of contemporary international law than you might imagine, for each one is taken directly from Hugo Grotius’s seminal work, The Law of War and Peace, published in 1625, widely regarded as the most basic brick in the foundation for modern public international law.

Another major founder of the law of war and peace, Francisco de Vitoria, lived a century before Grotius (1485 – 1546). Vitoria was a Spanish cleric and professor who taught in Paris and Salamanca during the time of the French Renaissance and the Spanish Inquisition. His interest in the international law of war and peace sprang from his concern about the Spanish Crown’s colonization of the Americas and, in particular, its violence against the native inhabitants.

A key question Vitoria examined in his work on war and peace was whether war can be justified on the basis that the people to be attacked do not share the religion of the attackers. He answered that question in the negative. Part of his reasoning was that religion is a matter of faith, and you cannot impose faith by fear and terror. If you try to do so, what you get is neither faith nor religion, but a fearful people who merely pretend to adopt your religion, which, Vitoria says, is sacrilege.

Vitoria was deeply concerned both with questions of jus ad bellum (just war) and questions of jus in bello (justice in the waging of war), but more so, with just war. After all, if wars can be prevented through the application of just war principles, there will be no need to worry about mitigating their horrible effects. That is as true today as it was in the Sixteenth Century.

Vitoria regarded the principle that innocents should be spared the violence of war as such a fundamental tenet of natural law that it applied not only to jus in bello questions, but also to jus ad bellum, or just war, questions. We see this in his answers to two questions: whether going to war can be justified on the basis of expansion of empire and whether war can be justified on the basis of anticipated future injuries. His answer to the first was that if war can be justified on the basis of expanding empire, then both belligerents could be in the right, that is, innocent. But because natural law forbids the killing of innocents, such a war is per se illegal.

As to whether war can be justified on the basis of anticipated future injuries — what we would call preemptive or preventive war – he answered that it cannot, because “offensive war is for the avenging of injuries and the admonishment of enemies . . . ; but there can be no vengeance where there has not first been a culpable offense,” and “we may not use the sword against those who have not harmed us [for] to kill the innocent is prohibited by natural law.”

Regarding jus in bello, Vitoria held that “it is never lawful to kill innocent people, even accidentally and unintentionally, except when it advances a just war which cannot be won in any other way,” and he stressed in this regard that care must be taken to ensure that the evil effects of the war do not outweigh the possible benefits sought by waging it. Therefore, if a fort or town that has many innocent people in it is not of great importance for eventual victory, it is not legal to attack it in order to defeat the combatants in it. Think of the bombings of London, Dresden, Tokyo, Hiroshima in World War II and the more recent attacks on Panama City, Lebanon, and Baghdad.

Finally, Vitoria was concerned not only with the application of natural law principles to actions taken against an enemy, but also their application to the people of the home state. In this regard, he opined that anyone whose conscience strongly dictates that he not participate in a war should not fight in it, even under orders from the prince (that is, even if drafted), because to such a person the enemy are innocent, and one may not lawfully kill an innocent person on any authority. Thus Vitoria proposes a broader scope conscientious objector option than any that has existed in modern times.

Grotius, building on Vitoria’s work on natural law, and in particular his precepts concerning the killing of innocents, wrote that while a country may have a legal right, strictly speaking, to kill innocents who are in an enemy fort, for example, or aboard a pirate ship, “what accords with a strict interpretation of right is not always, or in all respects, permitted. Often, in fact, love for our neighbour prevents us from pressing our right to the utmost limit.” Therefore, “the decision in such matters must be left to a prudent judgment, but in such a way that when in doubt we should favour that course as the more safe, which has regard for the interest of another rather than our own.” Grotius thus urges the equitable tempering of strict legal rights with the natural law principles of humaneness and compassion, in order to arrive at a decision about what is lawful in the broadest sense in the course pursuing a war.

Fast forwarding to the 18th, 19th and early 20th Centuries, two major aspects of the war of law and peace seemed to drop out of international law discourse more-or-less simultaneously: (1) just war considerations and (2) natural law principles. As we have seen, these elements were intimately bound up with each other before that, so in a sense it is not surprising they were discarded together. During this period, leading international law scholars such as the Swiss Vattel and the Dutch Bynkershoek advocated a “positivist” approach to law, essentially that international law consists only of what is written in treaties and what is established by international custom, nothing more. Nature and reason were excluded as a source of law. At the same time, state sovereignty became a dominant theme, and it was held to include the right of each independent state to decide for itself the rightness or wrongness of going to war. In other words, making war became a more-or-less uncontestable right of sovereign states, contrary to the teachings of Vitoria and Grotius. The double discarding of natural law and the just war doctrine may have had everything to do with the imperialism of the era, to which such considerations as the avoidance of war and the protection of civilians were inimical. Is that becoming the case again today?

Assume that Vattel,  Bynkershoek and their progeny are right in saying that only positive law – consisting of statutes, treaties, court opinions, and clearly established custom – is the only source of international law, or law in general. Assume further that some of the most important positive law documents use terms such as “dignity,” “humanely,” “cruel treatment,” “humiliating and degrading treatment,” “humanity,” “civilized peoples,” “fair.” All of these terms appear in the Geneva Conventions.  How are we to assign meaning to these terms, so as to make sure we do not violate the positive law that contains them? Don’t we ultimately have to resort to “principles of law considered as derived from nature [or] . . . reason . . . and considered ethically binding in human society” — that is, natural law? Don’t we find, upon digging below the surface, that even when such principles are put in the form of positive law, they still rely on and contain at their core, natural law principles? And if natural law principles contained in such undefined but important terms as “fairness” and “equality” can be relied on when they are placed in positive law documents, why can’t we rely on them before they are put in the form of positive law, or after the positive law in which they appear has been repealed?

Returning to the historical development of the law of war and peace, during the same period when positivists, statesmen, monarchs and other rulers were rejecting just war and natural law principles, there was a strong cross-current that embraced both natural law principles and, implicitly at least, just war principles. That cross-current consisted of the series of revolutions that began with the American Revolution and continued through the French Revolution and the revolutions of various Latin American colonies against Spain and Portugal. The United States Declaration of Independence begins, “When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature’s God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation. We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain inalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.” What are these fundamental principles on which the legal and political structure of the United States rests if not natural law? There is no reference here to any positive law — only to what are held to be self-evident truths, derived from the “Laws of Nature.” Many principles embodied in the U.S. Constitution, especially in the Bill of Rights, such as equal protection and the prohibition against deprivation of life, liberty or property without due process of law, seem to be derived from the natural law principles that clearly appear in the Declaration. Thus, natural law principles are built into the very fabric or United States domestic law. They were natural law principles before they became positive law, and I see no reason to say they lose that fundamental characteristic once they have been incorporated into positive law.

The same is true, as I have already suggested, of the contemporary international law of war and peace. As we have seen, international law and lawyers largely turned their backs on natural law and just war principles in the 18th, 19th and early 20th centuries, thereby providing a legal environment compatible with imperial conquest. But the horror and devastation of the two world wars caused a major re-thinking of this basic approach. This re-thinking led first, after World War I, to the Kellog-Briand Pact or the Pact of Paris, in which the signatory nations – including Germany, Italy, Japan and the United States – condemned war for the solution of international controversies, renounced it as an instrument of national policy, and pledged to settle international disputes only by peaceful means. Then, after World War II, this overturning of the doctrine of a right to wage war was carried much further by the Nuremberg Judgment and the United Nations Charter, as well as numerous other treaties and international declarations aimed in whole or in part at stopping war and/or at mitigating its violence and injustice, including the Geneva Conventions, the Genocide convention, and many others.

The UN Charter, perhaps the most important and as well as one of the most widely ratified of all the post World War II treaties, is full of principles which, if they are based on anything, must based on natural law. The preamble to the Charter, for example, refers to the “dignity and worth of the human person;” “equal rights of men and women and of nations large and small;” “fundamental human rights.” Article 1(2) refers to “the principle of equal rights and self-determination of peoples.” Article 2(3) refers to the settlement of international disputes only by peaceful means and in such a way that peace, security and “justice” are preserved. Aren’t these principles reminiscent of the principles that Jefferson expressly identified as deriving from natural law in the Declaration of Independence? And isn’t it true that, like the Declaration, the Charter puts them forth essentially as self-evident truths, that is, without any attempt to define them or to ground them in pre-existing treaties, constitutions, judicial decisions, or other positive law?

Now let’s look at what I believe nearly everyone would agree is the most basic purpose and principle of the UN Charter, the achievement and maintenance of international peace. This principle takes many forms in the Charter. For example, the preamble begins, “We the Peoples of the United Nations Determined to save succeeding generations from then scourge of war, which twice in our life-times has brought untold sorrow to mankind. . .” Later, the preamble refers to living together in peace as good neighbors, and to maintaining international peace and security. Article 1(1) states that a purpose of the UN is to maintain international peace and security and to take effective collective measures for the prevention and removal of threats to the peace and the suppression of acts of aggression. Article 2(3) states that all members shall settle their international disputes by peaceful means. Article 2(4), perhaps the most important, says, “All Members shall refrain in their international relations from the threat or use of force. . .” Under Art. 24(1), the Security Council has “primary responsibility for the maintenance of international peace and security.” And so on. What is the source of the Charter’s most fundamental principle – the achievement and maintenance of peace? Again, the Charter cites no positive law as a source. Don’t we necessarily fall back on the natural law of war and peace as Seneca articulated it so simply and eloquently two thousand years ago: “Just as the members of the body agree with one another, because preservation of each conduces to the welfare of the whole, so men refrain from injuring one another [for] we are born for community of life.”

By frankly recognizing the centrality of natural law concepts to the contemporary law of war and peace, we may be able to communicate more effectively with policy-makers and the people of the world who, after all, share some basic perceptions about such self-evident truths as equality, fairness, humanity, and peace.