This post is an advance version of a review essay that will appear in Humanity volume 10. It will be posted in five parts: one each day this week. This is part 3.
The Internationalists compellingly shows how the multi-layered nature of Old World Order made it difficult to undo all its principles at once. One of these principles was neutrality. Hathaway and Shapiro are not fans of it. They regard it as an “excuse” not to take action against aggressors and as a way to “make the world safe for war” (91, 96). In their view, neutrality prevented neutrals from helping victims of aggression by punishing perpetrators with economic sanctions. Indeed, trade discrimination violated the neutrals’ duty of impartiality in conflicts. Neutrals were either immoral, opportunistic, or both.
The modern condemnation of neutrality presupposes something that did not exist for most of human history: a generally shared category of aggression (and its implicit opposite, victimhood). If international aggression is real, identifiable, and a crime, then it is logical to think that states cannot and should not be allowed to remain impartial towards it. Yet the notion of aggression had no legal existence before Article 10 of the League Covenant first introduced it in 1919. Most countries that invoked neutrality prior to that time were not interested in punishing a vice that was still undefined. The point of neutrality was to obtain protection. Neutrals saw their international legal status as a blessing that served to limit war, not expand it. So while Hathaway and Shapiro are right to argue that “the law of neutrality depended on the legality of war,” the reverse is equally true: war was tolerable as a legal institution precisely because most states in the world could opt out of conflicts that did not politically or materially concern them (170).
At the heart of the matter is whether one sees neutrality primarily as an obligation (not to take sides when one is partial) or as a right (not to have to take sides when one does not want to). For the United States, neutrality was indeed a form of having it both ways; separated from the Old World by two oceans, the country could both preserve its prosperity and stay out of inter-European wars. But for almost all other countries, neutrality was an essential way to contain the inevitable damage wrought by war, especially its effects on trade and food supply. The danger was not that aggression—a non-existent category at the time—would go unpunished, but that belligerents would find ways to coerce neutrals into joining the war, or simply invade them. To small states like Denmark, Switzerland, or Belgium, at perpetual risk of occupation and dismemberment, the point of declaring oneself permanently neutral was to preserve their existence as independent states. Some neutrals such as the United States were, as Hathaway and Shapiro depict, large spoiled states who wanted to have their cake and eat it too; but most were small countries that used international law to limit war and obtain protection from its ravages.
Once the introduction of the notion of aggression began a slow moralization of inter-state war in the international system, neutrality was bound to come under severe pressure. Hathaway and Shapiro provide a gripping and insightful account of the way that the United States negotiated its traditional neutral stance in the aftermath of Kellogg-Briand.
Disputes about neutrality were often economic, and traditional neutrality had to be dismantled if economic sanctions were to come into their own. Hathaway and Shapiro accurately identify gunboat diplomacy as a part of the Old World Order, a practice that gave way to economic sanctions in the New World Order. On closer inspection, however, the difference between these practices turns out to be more cosmetic than supposed. Economic sanctions predated the Kellogg-Briand Treaty by at least a decade. They first became a formal part of the international system when they were enshrined in Article 16 of the League Covenant. It is true, as Hathaway and Shapiro note, that in the interwar period economic sanctions remained a somewhat incomplete and contested element of international institutions. But this had less to do with the strength of the internationalists behind them than with the legal transformation that economic sanctions entailed.
What was at stake in this transformation was whether the coercive economic isolation of a country constituted an act of war. This mattered because in the Old World Order the existence of a state of war was, as Hathaway and Shapiro underscore, the only way to obtain belligerent rights. To impose a naval blockade was clearly a form of coercion, and since the time of Grotius it had been understood as an act of war that created a state of war and conferred belligerent rights. In other words, it was impossible to economically isolate a sovereign state without legally creating a state of war. The 1856 Paris Declaration made explicit the international law of blockade, the most basic rule of which was that for a blockade to be legal, it had to be announced officially and maintained effectively, and this required first declaring war.
There was one exception to this: from the 1830s onward Britain and France began to enforce treaty rights in so-called “pacific” blockades, that is, they would commence a blockade without declaring war. This was in essence a form of gunboat diplomacy, and sometimes it led to short undeclared de facto shooting wars. Pacific blockades did not create a state of war because the balance of forces was so unequal that there was no need for the imperial powers to declare one. However, the jurists who were codifying international law after the 1870s overwhelmingly rejected pacific blockade as an unlawful practice. Of course, this did not much trouble the European great powers, for whom international law was not only an instrument of intra-European peace, but also a tool of pressure against non-European states.
Together with pacific blockade, lawyers and statesmen in late nineteenth-century Britain and France also began to speak more frequently about “sanctions.” They used this term to refer to the enforcement measures built into various treaties and contracts. In domestic affairs, these were juridical in nature. Yet in the international realm of colonial expansion, sanctions could have a coercive or even military character. Such an ultimate backstop was applied to the Ottoman Empire in 1881, when Constantinople’s default on its debt to the Western Powers was used by Britain to trigger so-called “super-sanctions.” This resulted first in the takeover of the empire’s public finances by European creditors, and one year later in the military invasion and occupation of Ottoman Egypt.
The dismantling of sovereignty followed by occupation was therefore an accepted way to enforce inter-state treaties and even private economic contracts between European creditors and non-European debtors. Hathaway and Shapiro see all this as part and parcel of the violent and nasty Old World Order. There is no legal-philosophical difference to them between the British occupation of Egypt and, say, the Crimean War. But to the Western powers these conflicts were conceptually different: colonial wars were not quarrels between two equal parties with the verdict of battle as the arbiter, akin to a civil law dispute. They were considered punishments, or at best policing actions. Besides this hierarchical difference in kind, such short wars and occupations were often undeclared. European powers did not consider “uncivilized” opponents to be legal equals and thereby entitled to belligerent status. Before the Old World Order had come to an end, a new range of undeclared de facto wars, interventions, and occupations was therefore emerging, cast in the language of civilization, underwritten by international law, and enforced with violent “sanctions.”
The creation of the League of Nations in 1919 marked a watershed moment in the international law of neutrality and aggression, and the start of the history of economic sanctions properly so-called. The innovation of the victors of World War I was to turn the techniques of economic warfare used by the Entente against the Central Powers into disciplinary actions that the League of Nations would enforce in peacetime. Sanctions were the new go-to punishment for aggression. But imposing a blockade would no longer necessarily create a state of war, as it had done before. The techniques of economic warfare had moved from the legal realm of war to that of peace. Furthermore, Western countries could now use economic sanctions against each other. Sanctions were no longer a purely colonial tool for the preservation of order. Unsurprisingly, when Germans protested in the 1920s about the harsh enforcement of the Versailles Treaty, they complained that their country was being “Ottomanized.”
The Internationalists is right to see economic sanctions as central to the international order after 1945. Yet as an element of the New World Order they antedated Kellogg-Briand. Since the League of Nations introduced non-belligerent blockade into international law, the use of such economic pressure has risen both by individual states (unilateral sanctions) and through regional or international organizations (multilateral sanctions). Yet their legal novelty should not mislead us as to the form and effect of modern sanctions, which resemble the universalization of nineteenth-century practices of pacific blockade. As a policy instrument sanctions can indeed be an alternative to war. But they became an alternative not just by shrinking the definition of war (to self-defense), but also by expanding what was allowed in times of peace.
Hathaway and Shapiro ignore this redefinition of the boundary between war and peace when they praise the rise of “outcasting” through economic sanctions. Besides an alternative to war, sanctions can also be a covert form of war or even a prelude to war. The consequences of outcasting Saddam in the 1990s were mass civilian death and included the launching of cruise missiles and air strikes against Iraq for non-compliance with UN Security Council resolutions, all without a declaration of war. When the United States invaded Iraq in 2003 without either UN authorization or a clear ground for self-defense, it showed once more that outcasting all too often remains parasitic on the use or threat of force. 
While Hathaway and Shapiro at least acknowledge that the Iraq sanctions caused “humanitarian complications”—an impressive understatement—they obscure matters more seriously by arguing that the 2015 Iranian nuclear agreement was an exemplary success of peaceful outcasting (388). In fact, both the threat of military force (the prospect of an Israeli air strike on reactor sites), the use of covert tactics (the assassination of nuclear scientists), and acts of aggression in new and legally unregulated domains (the use of the specially designed Stuxnet virus to blow up uranium-enriching centrifuges) were crucial in dissuading the Iranians from furthering their nuclear program. A mix of economic sanctions, threats of war, and the 21st-century equivalent of gunboat diplomacy compelled Iranian assent to the nuclear deal. As it turns out, outside the West the habits of the Old World Order die hard. Sanctions also present difficulties for Hathaway and Shapiro’s claim that with the advent of the New World Order “a coerced agreement was no agreement at all”—for what are sanctions if not coercive measures (304)?
The shift from collective responsibility to individual responsibility for war has allowed the prosecution of political and military leaders from Nuremberg, for crimes against peace, to The Hague. Hathaway and Shapiro rightly emphasize this change as an important and laudable shift. Yet economic sanctions are still overwhelmingly used as forms of pressure at the collective level. Even when they target individuals, the effects are usually deflected onto civilian populations and the less fortunate in society. Despite being praised by the U.S. foreign policy establishment, it is not clear that “smart sanctions” have helped to preserve peace any better than “smart bombs” have protected human rights.
 On the groundbreaking nature of the 1856 Treaty of Paris—the first multilateral international treaty open to signature by any country willing to abide by its provisions—see Jan Lemnitzer, Power, Law and the End of Privateering (New York: Palgrave Macmillan, 2014).
 The states, islands, and ports placed under pacific blockade included Argentina (1838-1840 and 1845-1850), Bolivia (1879), Brazil (1862-1863), Cartagena (1834), Crete (1897), Formosa (1884-1885), Gaeta and Messina in Sicily (1860-1861), Greece (in 1827, 1850, and 1886), Mexico (1838), New Granada (1837), the Netherlands (1832-1833), Nicaragua (1842 and 1844), Portugal (1831), and San Salvador (1842), Siam (1893), Venezuela (1902-1903), Zanzibar (1888-1889). The only existing works on this practice are Albert E. Hogan, Pacific Blockade (Oxford: Clarendon Press, 1908), and Horst P. Falcke, Le blocus pacifique (Leipzig: Rossberg’sche Verlagsbuchhandlung, 1919).
 Lassa Oppenheim, International Law: A Treatise, 3rd Ed., Vol. II (London: Longmans, Green & Co., 1921), 56.
 Kris J. Mitchener and Mark D. Weidenmier, “Supersanctions and Sovereign Debt Repayment,” Journal of International Money and Finance 29, no. 1 (2010): 19–36.
 Two useful overviews of political science and international relations research into the field are Gary C. Hufbauer, Jeffrey J. Schott, Kimberly A. Elliott, Barbara Oegg, eds., Economic Sanctions Reconsidered, 3rd Edition (Washington, D.C.: Institute for International Economics, 2008) and Peter Wallensteen, A Century of Economic Sanctions: A Field Revisited (Uppsala: Universitetstryckeriet, 2000). For a good history of sanctions since the 1930s from a U.S. perspective, see Alan P. Dobson, US Economic Statecraft for Survival 1933-1991: Of Sanctions, Embargoes and Economic Warfare (London and New York: Routledge, 2002). The best (relatively international) economic history of the maritime aspects is Lance E. Davis and Stanley L. Engerman, Naval Blockades in Peace and War: An Economic History Since 1750 (Cambridge: Cambridge University Press, 2006). The European and international history of economic sanctions after World War I is the focus of my own current research.
 There was an interwar attempt to include blockades and other forms of economic strangulation in the definition of aggression. Proposed by Soviet foreign minister Maxim Litvinov as an “economic non-aggression pact,” the idea was rebuffed by the Western great powers. Still, the Soviets signed a series of multilateral treaties defining aggression (including, among others, invasion, aerial attack, naval blockade, and support for irregular armed forces in other states) with their neighbors in Eastern Europe, the Black Sea region, and Central Asia in the 1930s. It would remain the only extant definition of the term in the interwar period. Despite outlawing it in the Charter’s Article 1, the UN did not substantively define aggression until 1974. Only in 2010 did a broad-based international definition of the crime of aggression emerge with the Kampala Amendments to the Rome Statute that created the International Criminal Court.