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The surprising legacy of a ninety-year-old peace pact

Discussed in this essay:

The Internationalists: How a Radical Plan to Outlaw War Remade the World, by Oona A. Hathaway and Scott J. Shapiro. Simon & Schuster. 608 pages. $30.

How to Do Things with International Law, by Ian Hurd. Princeton University Press. 200 pages. $29.95.

A Foreign Policy for the Left, by Michael Walzer. Yale University Press. 216 pages. $30.

In 416 bc, midway through the Peloponnesian War, a powerful force landed on the island of Mílos. Though technically a Spartan colony, Mílos had stayed out of the decades-long war between Athens and Sparta. No longer willing to tolerate such neutrality, the Athenians delivered an ultimatum: surrender or be annihilated.

Sturmtruppe geht unter Gas vor (“Shock Troops Advance Under Gas”) from Der Krieg (“The War”), by Otto Dix © Artists Rights Society, New York City/VG Bild-Kunst, Bonn/The Museum of Modern Art/SCALA/Art Resource, New York City

The Melians were outraged. Refusing to submit to unprovoked aggression, and hopeful that the righteousness of their cause would provide a bulwark against the Athenians, the islanders dismissed the envoys. It would prove to be a costly decision. As Thucydides tells it, Athens promptly overran Mílos, put all the grown men to death, “and sold the women and children for slaves.” The Athenians provided a blunt explanation for their actions: “The strong do what they can, and the weak suffer what they must.”

For centuries, this brutal logic governed relations between the European nation-states: war was a perfectly legitimate way of redressing perceived wrongs. The system came to a crashing halt on August 27, 1928, when representatives from fifteen nations gathered in Paris to sign the Kellogg-Briand Pact, which in two neat sentences outlawed war and dramatically changed the world for the better. That, in any case, is the bold claim made by Oona A. Hathaway and Scott J. Shapiro, professors of law at Yale, in The Internationalists, a five-hundred-page attempt to portray Kellogg-Briand as “among the most transformative events in human history.”

At first glance, their argument seems absurd. In recent decades, those who have bothered with Kellogg-Briand have treated it as a naïve and irrelevant document. George F. Kennan, the brilliant Cold War statesman, dismissed it as “childish, just childish.” Ian Kershaw, a prominent historian of the Third Reich, described it as “singularly vacuous.” And J. L. Brierly, the British legal scholar whose Law of Nations instructed a generation of international-law students, makes virtually no mention of it at all.

The Internationalists begins the formidable task of pushing back against this consensus by taking us to early-seventeenth-century Holland, where Hugo Grotius, a prodigy who had entered university at the ripe age of eleven, penned On the Law of War and Peace, the first systematic treatise on the subject. Having witnessed “throughout the Christian world . . . a lack of restraint in relation to war, such as even barbarous nations should be ashamed of,” Grotius insisted that the natural law of nations places limits on that license. States, he argued, may go to war only in response to a threatened or actual wrong, and when no peaceful alternative exists. Wars waged to correct a wrong or to defend a right are just; those waged simply to seize territory or treasure are unjust.

For all his elaborate discussion of what makes war just, Grotius concluded that international law did not permit a third party to determine when a sovereign’s rights had been violated. In this respect, the just-war requirement was hollow — every sovereign could decide for himself the justness of his cause, and no other could question that decision.

Hathaway and Shapiro locate in Grotian theory the legal framework for Europe’s Old World Order, a system that tolerated and even rewarded aggression. Any sovereign who felt that a rival had wronged him was authorized to invade. That said, the Old World Order was not entirely bereft of rules. Because it barred third parties from weighing the justness of a belligerent’s cause, the Grotian system required the observance of strict neutrality by non-warring states. Condemning or punishing a belligerent was forbidden, as it would turn the third party into a belligerent itself. Similarly, to begin trading with one party to a conflict but not the other violated the terms of neutrality.

The system placed another constraint on sovereign behavior, namely on the level of public rhetoric. For several centuries, nations used “war manifestos” — part legal briefs, part PR documents — to lay out their reasons for resorting to force. Hathaway and Shapiro canvass some four hundred of these, and two things become clear: first, that nations were eager to avoid the ignominy of appearing to go to war without justification; and second, that almost anything could supply that justification. Protecting trade interests, defending missionaries, enforcing dynastic succession, all sufficed to justify war; in 1492, soon-to-be Emperor Maximilian I offered as the reason for war against France the fact that King Charles had stolen his wife. By the late nineteenth century, all wars had come to be seen as equally lawful.

The First World War represented a massive shock to the Grotian system. The Hague Conventions of 1899 and 1907 had concerned themselves primarily with jus in bello (“laws of war”), the norms that describe how armies should conduct themselves on the battlefield. These conventions prohibited, for example, the use of dumdum bullets and other projectiles that “expand or flatten easily in the human body.” But the unprecedented horrors of World War I — the staggering futility of trench warfare, the sheer waste of men and matériel — suggested that discussions about the laws and norms of war were not enough. War itself, and not simply outrages in battlefield conduct, was the catastrophe.

And so was born the effort to declare war illegal. As Hathaway and Shapiro tell the story, it was spearheaded by Americans such as Salmon Levinson, a corporate attorney with little training in international law who framed the “simple but profound idea” that the “real disease of the world” was the legality of war, and the senators Philander Knox and William Borah. In 1921, these men wrote a pamphlet for the freshly minted American Committee for the Outlawry of War that declared war a “public crime.” These first steps, along with the work of a Columbia historian named James Shotwell, found their way into the 1924 Geneva Protocol, which declared aggressive war “a violation of the solidarity” of nations and an “international crime.” (Ultimately, the document was never ratified.)

These efforts culminated in the Kellogg-Briand Pact. Hathaway and Shapiro view it as a stunning achievement, but even at the time, not everyone was convinced. Edwin Borchard, a professor of law at Yale, predicted that it would accomplish nothing. Although the pact declared a blanket ban on war, the signatories had insisted that the absolutist language could not be construed to restrict a nation’s right to defend itself against aggression, which was left undefined, so it failed to specify the conditions that justified wars of self-defense. “It would be difficult,” Borchard noted ruefully, “to conceive of any wars . . . that cannot be accommodated under these exceptions.”

If Kellogg-Briand was supposed to make the world a more peaceful place, it failed spectacularly — at least in the short term. Scarcely a decade after it was signed, imperial Japan and Nazi Germany catapulted the world into the most lethal war in human history. What are we to make of such extreme acts of military predation by two of the pact’s first signatories?

Hathaway and Shapiro offer an intriguing answer. They remind us that Japan had been rudely introduced to the Old World Order in the early 1850s, when Matthew Perry, a US Navy commodore, forced the isolated nation into trade relations at the barrel of a gun. Such “diplomacy” was fully consonant with the Grotian system, and Japan proved a studious pupil. Yet no sooner had the Japanese mastered the rules — in attacking Pearl Harbor, Hathaway and Shapiro contend, Japan was “simply following the law of nations that U.S. Commodore Perry . . . had introduced” — than the rules changed.

The authors hazard a similar explanation for German aggression, arguing that in claiming Eastern Europe as part of Germany’s “sphere of interest,” Hitler was inspired by the United States’ Monroe Doctrine, the muscular article of American foreign policy that in the early 1820s declared the Western Hemisphere a zone of exclusive US interest. The author’s theory does not, however, wash in this case. The Old World Order may have permitted virtually all forms of militarism, but Hitler’s Vernichtungskrieg (“war of annihilation”) would have failed even under these highly permissive standards. The Allies did not go to war against Hitler to enforce the rules of the New World Order established by the Kellogg-Briand Pact. They fought Hitler because he broke all the rules.

Hathaway and Shapiro’s account of how the Allies reckoned with the war after its end — in the courtroom in Nuremberg — is no less problematic. Nuremberg was history’s first international criminal trial. The indictment charged the twenty-one Nazi leaders in the dock with war crimes and crimes against humanity, but the gravamen of the prosecution’s case was that the defendants had committed “crimes against peace” — that they had planned and waged a war of aggression in violation of international law and treaties.

For the first time, a court was asked to hold leaders of a state criminally liable for doing what sovereigns had done legally for centuries. Given the unprecedented nature of the charge, it was inevitable that some critics would insist that “crimes against peace” violated the solemn bar against trying persons with retroactive law. For while Kellogg-Briand might have declared war illegal, it had stopped short of declaring it a crime for which individuals could be held accountable. Even André Gros, the French jurist who helped to write the trial’s charter, conceded that the crime of aggressive war was the “creation” of the four people who had drafted the Nuremberg charter, who were, after all, “just four people.”

Hathaway and Shapiro argue that Nuremberg’s criminalization of aggressive war posed no problems of retroactivity, since it represented less a radical innovation than a consolidation of the New World Order. They chastise the Nuremberg judges, world-class legal minds, for failing to appreciate this in their written judgment, insisting that the tribunal “was uncomfortable with its own decision.” But if there was any discomfort in the Nuremberg judgment, it arose because the judges understood that in convicting Nazis of crimes against peace they were not applying law — they were creating it.

More troublingly, in their effort to prove that Nuremberg simply consolidated a legal reality, Hathaway and Shapiro completely ignore the unhappy afterlife of the incrimination. If Nuremberg was the first trial to treat aggressive war as a crime, it was also, in a sense, the last. The overwhelming majority of convictions secured in the so-called successor trials conducted by the American military were not for crimes against peace but for war crimes and crimes against humanity. And while the Tokyo war crimes trials convicted several Japanese statesmen and generals of waging a war of aggression, they did so over the forceful seven-hundred-page dissent of Radhabinod Pal, an Indian judge who condemned the incrimination as retroactive, imprecise, and partisan — in short, a law concocted by Western lawyers to entrench a status quo that was the result of centuries of Western aggression.

The charge of crimes against peace has not fared much better in recent decades. The International Law Commission, a body of international scholars and jurists convened by the UN General Assembly, tried in the early Fifties to offer an adequate definition of aggression but failed. So vexing was the effort — Did wars of colonial liberation constitute aggression? What about fomenting civil strife in another country? — that the jurists argued vehemently about whether a definition was even possible or necessary. Several years later, an attempt to draft a legal document, “Offences Against Peace and Security of Mankind,” stalled in the General Assembly. In the early Nineties, the UN established ad hoc tribunals — the first international criminal courts since Nuremberg and Tokyo — to deal with atrocities in the Balkans and Rwanda; neither court included aggression as a justiciable crime.

In 2002, a permanent institution meant to supplant the ad hoc tribunals, the International Criminal Court in The Hague, opened for business. Hathaway and Shapiro assert that the “crime of aggression is now one of the four crimes that can be prosecuted before the ICC” — but this is patently false. In fact, the drafters of the ICC’s statute struggled over a definition of “crime of aggression” and specifically withheld the court’s jurisdiction until that problem had been solved. In 2010, after years of difficult negotiations, jurists declared victory, and yet the ICC’s state parties have yet to activate the court’s jurisdiction.*

If wars of aggression have indeed become less common since 1945 — and Hathaway and Shapiro marshal an impressive range of data to support this claim — it is not because would-be aggressors have feared being hauled before an international court. Rather, the ban on aggression has been enforced by what the authors call outcasting — isolating transgressing states through economic sanctions and the withholding of international trade. However, outcasting has done little to reverse Russia’s annexation of Crimea, and, as the US election of 2016 made abundantly clear, the practice can invite powerful retaliation.

Interstate war may have declined of late, but intrastate wars have more than adequately filled the gap. As for Hathaway and Shapiro’s insistence that, even factoring in such conflicts, the world has been made more peaceful, one is reminded of Bertrand Russell’s inductivist turkey, which observes its feeding pattern and confidently concludes, “I am always fed at 9 a.m.” This holds true until Christmas Eve, when it has its throat slashed. From 1871 to 1914, Europe experienced its longest period of continuous peace since the Roman Empire, leading many contemporaries to believe that increased trade and democratization had rendered war a thing of the past. Gobble, gobble.

Only at the end of The Internationalists do the authors consider the fragility of the ban on war. Kellogg-Briand made no allowances for wars of self-defense. The UN Charter of 1945, by contrast, does make such an exception, but only in the case of an armed attack; it does not allow for preemptive strikes. International law now appears to see things differently, permitting unilateral action in cases of real or imminent attack. As Hathaway and Shapiro acknowledge, this trend threatens to make self-defense the “exception that swallows the rule.”

Self-defense is a central concern of Ian Hurd’s new book, How to Do Things with International Law. Hathaway and Shapiro are law professors, so perhaps it is unsurprising that they see the law as a powerful restraint on state power. Hurd, a political scientist at Northwestern University, is more skeptical. His slim volume is a contribution to “lawfare,” a new field that views the law of armed conflict not simply as a restraint on state militarism but as a tool that states can exploit to their tactical and strategic advantage. As Hurd writes, international law may “reduce coercion and destruction, and it may strengthen states’ ability to make war.” He does not deny that “states feel pressure to frame their actions as rule-abiding and consistent with their legal obligations.” The point is that when they make use of legal rhetoric, they reap the political benefit of being able to do largely as they please. Law and legal argument, shrewdly wielded, are means of aggression.

In a chapter called “The Permissive Power of the Ban on War,” Hurd directly addresses the self-defense exception to the prohibition on war-making. Under the terms of the UN Charter, the threat or use of force by a state is illegal unless it is deployed in self-defense or is authorized by the UN Security Council. But what exactly does “threat or use of force” mean? Does it include embargoes? What if the aggressor is not a state but a terrorist group? The problem is that states — especially the most powerful ones — answer these questions for themselves.

A similar problem applies to the question of imminence. Traditionally, imminence has been understood to mean “instant, overwhelming, and leaving no choice of means, and no moment for deliberation.” In 2006, the Bush Administration adopted a far more expansive definition, arguing that

the greater the threat, the greater . . . the risk of inaction — and the more compelling the case for taking action to defend ourselves, even if uncertainty remains as to the time and place of the enemy’s attack.

Was the US invasion of Iraq an illegal act of aggression or a legitimate application of the Bush doctrine of self-defense in response to a perceived imminent threat? Here again, there is no answer, since there is no world government to say that Bush was wrong. Even the “self” in “self-defense” has been dramatically expanded, as it no longer applies exclusively to a nation’s territorial boundaries but has taken on a functional meaning loose enough to justify, for example, military strikes to bring down Muammar Qaddafi in Libya.

A law that fails to distinguish compliance from noncompliance is no law at all. It is not clear that the UN’s ban on war can make that distinction. According to Hurd, if “states make their own judgments about the threats they face, then the ban on war has become ‘law that cannot be broken.’ ” Self-defense has thus become for the New World Order what “defending a right” was for the Old — a catchall that can be used to justify any and every recourse to arms. Even the war manifestos of earlier centuries included self-defense as a justification for war in some seventy percent of cases.

No less knotty are the problems raised by so-called wars of humanitarian intervention. In the spring of 1999, NATO waged an air war against the Federal Republic of Yugoslavia. Launched without the authorization of the UN Security Council — Russia would have vetoed it — the war was attacked by critics around the globe as an act of international aggression. NATO, for its part, insisted that military intervention was necessary to put a halt to ethnic cleansing by the Serbs. When force is used to “prevent an overwhelming humanitarian catastrophe,” the British government claimed before the UN Security Council, “military intervention is justified.”

Michael Walzer agrees. In his new collection of essays, A Foreign Policy for the Left, the eminent political theorist delivers a full-throated defense of humanitarian intervention. The book lacks the heft, richness of example, and systematic argumentation that made his Just and Unjust Wars (1977) an indispensable text, but it displays many of the virtues that have long distinguished Walzer as a leading thinker about war — most notably his ability to frame clear ethical judgments that avoid the postures of both the saint and the cynic.

In A Foreign Policy, Walzer makes the case that humanitarian intervention is justified even when carried out unilaterally and in the absence of a UN mandate. Such interventions, however, must satisfy several conditions. They should not be undertaken in response to every human rights abuse, only to stop mass atrocities. (“Pol Pot’s killing fields had to be shut down, by a foreign army if necessary.”) The goal should be modest — to stop the killing, not to hang around and engage in regime change. This means, furthermore, that force must be ethically deployed: you “cannot attack a murderous government, with all the consequences that that has for its citizens or subjects, while insisting that your own soldiers can never be put at risk.” That, in large measure, was the problem with the air war against Yugoslavia, which relied on imprecise, high-altitude bombing to insulate NATO pilots from the risk of being shot down, and so resulted in numerous civilian casualties.

Nevertheless, by insisting that wars of humanitarian intervention require us to put our soldiers at risk, Walzer raises more questions than he answers: What level of risk is required? Who gets to define when intervention is necessary? When war is waged in response to the outraged conscience of humanity, domestic support for such interventions will be thin, even if at first it is broad. Thin support means domestic popular opinion will not tolerate our soldiers dying in great numbers to protect the victims of a far-flung state. Should this fact enter into our military plans? And if so, how? And how should this influence our use of Predator drones and other technologies that essentially make war riskless for our population?

The point goes further still. When war is waged to put an end to atrocities, our adversaries cease to be ordinary combatants. They are criminals, either actively perpetrating or aiding and abetting international crimes. Once the enemy is understood as a criminal, he ceases to enjoy the combatant’s privilege to lawfully resist our intervention. He has no more right to fire a weapon at our soldiers than does an ordinary murderer to shoot at the police. In this sense, not only are wars of humanitarian intervention permissible, opposing them is a criminal act. War has become a tool of policing.

Hathaway and Shapiro see things very differently. While never addressing the question of the NATO air war directly in their book, they insist that as a strict matter of law, wars of humanitarian intervention are illegal and should remain so. It is better, they insist, “to live in a world where war is not a permissible mechanism for righting wrongs, even if that means some wrongs remain unaddressed.”

Their conclusion is hardly indefensible, but what makes it troublesome is that for all the granular legal history packed into their sizable tome, they never actually examine — as Walzer has — the most fundamental issue: What purpose does the ban on war serve? Is its aim to safeguard the sovereignty and the territorial integrity of nation-states? Or is it meant to protect human beings from the scourge of armed conflict?

In failing to address this question, Hathaway and Shapiro end up embracing a rule without a rationale. If they believe the ban on war is a way of protecting nation-states against bad neighbors, they need to tell us why the interests of states should trump the rights of persons. If, however, they believe the ban is ultimately about protecting people from mass violence, why would they not carve out an exception for wars of humanitarian intervention? As Václav Havel wrote at the time of the NATO sorties, “Defending human beings is a higher responsibility than respecting the inviolability of the state.”

is the James J. Grosfeld Professor of Law, Jurisprudence, and Social Thought at Amherst College. His most recent book is The Right Wrong Man: John Demjanjuk and the Last Great Nazi War Crimes Trial (Princeton University Press).

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