Alberico Gentili may rightly be said to be the first secular interpreter of international law. Gentili, born in northern Italy in 1552, the son of a physician, studied law at the University of Perugia, where he took his doctorate. He began practice in his native country, the March of Ancona. But he and his father, having become Protestants, were forced to flee Italy in 1579 just ahead of the Inquisition, which sentenced them in absentia to penal servitude for life and confiscated their property. From Austria and Germany, the Gentilis came to London in 1580, after which the son became a lecturer on civil law at Oxford University.
In 1584—the year of the assassination of William the Silent*—Gentili was asked for a legal opinion in the sensational case of Mendoza, the Spanish ambassador involved in the Throckmorton conspiracy to murder Queen Elizabeth. Contradicting the opinion of the Privy Council, Gentili held that Mendoza was protected by ambassadorial immunity and thus could not be tried by an English court. His conclusion, which defied public opinion of the day, was accepted by the government, and Mendoza was deported. With lawyerly economy, Gentili converted his memorandum into the treatise On Embassies, published in July 1585 and dedicated to his patron, Sir Philip Sidney.
Gentili left England the following year for Wittenberg but was recalled to Oxford to become Regius Professor of Civil Law, a post he held until 1600. For his inaugural lecture as professor in 1588, the year of the Armada, Gentili had chosen the timely subject: “Whether the subject of a prince whose religion is different from his may take up arms against a prince of his own creed, in other words whether a Catholic may legitimately fight against [a Catholic sovereign] in the service of his sovereign [Protestant] Queen.”27
Gentili answered this question in the affirmative, in contrast to what might have been expected of the sectarian princely state. His lecture, the Commentatio Prima on the law of war, was followed by the Commentatio Secunda and Tertia in 1589, that, much revised, form the three books of the De Jure Belli, Gentili's masterpiece. In 1600 he began practice at Gray's Inn, ceasing to be a law professor. In 1605, he became counsel for the Spanish Embassy, defending Spain against claims made before the British Admiralty Bar by Holland, arising out of their war. This is sometimes thought paradoxical28—Gentili was, after all, a Protestant refugee—but it was entirely consistent with his approach to the role of international law.
Gentili recognized the arrival of the society of princely states that formed the basis of international law in the sixteenth century, and referred to the “general law of all kingdoms which comes into being with kingdoms themselves and, as it were, by the law of nations.”29 He defined war as a conflict between armed forces of a state, thus discarding the private wars of medieval princes. This view is especially evident in his treatment of treaties. In the medieval period, before the emergence of states, treaties were considered binding only during the lifetimes of the signatories. Gentili held that now treaties were binding on the successors of signatories, as well as upon the peoples of the parties to the treaty.
Moreover, consider his treatment of the problem of duress in treaties. First, he argued that treaties are not the mere contracts of princes; they bind the State, and thus even the treaty made under duress is binding. A defeated prince cannot annul a peace treaty on the ground that he was compelled to agree to it.30 Second, Gentili further distanced the State from the person of the prince by arguing that, even in the absence of coercion, an agreement made by a captive prince is not binding if it inflicts a severe injury on the State. Thus there are inherent limitations on the power of princes to alienate sovereignty.31 And he goes further to recognize the society of states by asserting that there are common interests (“commune ratione et pro aliis”) that will serve as a legal basis for making war.32
Gentili's interest to us, however, lies not merely in his recognition of the post-Augsburg legal world as one in which a society of states has come into being, but also in his understanding of the shortcomings of that society and of its constituent elements, the princely states.
Princely states were ferociously sectarian and potentially incoherent (because they were composed by a kind of dynastic roulette and had no necessary national basis); they lacked a completely centralized authority (because they had not achieved financial independence from the various subparts of their holdings) and had so little juridical sense of themselves that the potential for international agreements to strengthen the State was limited to the advantages wrung by war and expressed in treaties of doubtful duration. Gentili's writing attempted to shore up the system of such states by addressing each of these difficulties.
Nussbaum calls Gentili the “originator of the secular school of thought in international law,”33 and this is surely right. We have to see this in its context, however, to appreciate how Gentili sought to bring this about. He did not distinguish between ius gentium and ius natural, and indeed deliberately identified the ius gentium with the ius natural, both being an expression of divine will. Gentili was a devout Christian and could hardly have taken any other position. Rather, having accepted this substantive ontology, he then proceeded to distinguish those matters that were justi-ciable by lawyers and those that had to be referred to the clergy. Repeatedly he insists on the distinction between the respective jurisdictions of the juris consulti and the theologi.* By this means he managed to narrow the scope of ecclesiastical decision to those matters concerning the first three of the Ten Commandments, and indeed largely stripped international law of the moralizing basis it had previously had, in favor of a juridical one. Perhaps his most famous remark is “Silete theologi in munere alieno.”* He excludes from the just causes of war opposition to the Christian faith or interference with proselytizing. He refuses to recognize any arbitral power of the pope, preferring instead to refer international arbitrations to “experienced judges.”34
As is sometimes the case with the expatriate, Gentili was acutely sensitive to the ties of national culture and consanguinity. Arguing that a state, though not itself attacked, is obliged to aid an ally even beyond the terms of an existing alliance when the ally is unjustly attacked, Gentili goes even further and also urges that aid ought to be given to those states, whether or not they are allies, that are similar to the state in question with respect to race, blood, or religion. This invites moral relativism, of course, and Gentili does not shrink from this. He breaks decisively with the moral tradition of the scholastics by holding that a war may be just on both sides. Moreover, he concurs with Ayala that the just treatment of prisoners is not a matter of the justness of the war. By these moves, Gentili is able to argue for the humane treatment of prisoners on both sides of a conflict, i.e., whether or not the state of which they are subjects is at fault, and whether or not the oppressing state can be said to be just in its aggression. Taken together, these doctrines encourage the State and its subjects to more closely identify with each other.
The most important contribution of Gentili to the law of nations is his principle that a treaty is only binding so long as the conditions within which it is to operate have not fundamentally changed. This doctrine— clausula rebus sic stantibus—remains an important idea in international law. It is the complementary principle to the doctrine pacta sunt servanda (treaties are to be observed). One can see how these two fundamental ideas are given life by the society of modern states: the latter when treaty obligations are objectified and extended beyond the person of the prince or signatory; the former enabling states to behave according to their interests and not as a matter of personal, moral obligation. One can scarcely imagine recognition by the society of states of the ragione di stato of Machiavelli's princely state without something like the expediency of the clausula.
Gentili provided the society of princely states with an interpretation of its constitutional basis that addressed the weaknesses of that form of the State. Secularism, nationalism, and rationalism all were therapies much needed by the princely state. And in one more respect, Gentili sought to buttress that State. This was his adherence, which grew throughout his life, to greater forms of monarchical absolutism, anticipating (like the “therapies” just mentioned) the advent of the kingly state.
In his posthumously published Pleas of a Spanish Advocate, Gentili especially concentrates on subjects drawn from maritime disputes. He strongly advocates freedom of the seas and condemns states and nonstate actors who interfere with commerce in international waters. At the same time he reserves to the sovereign a dominion over the coastal waters extending to one hundred miles at a time when three miles—the range of a cannon—was the commonly accepted term. Nor was this an aberration. His service to Spain, which appeared to many so strange in the context of his personal history, seems less bizarre if it is remembered that Gentili sought, and was granted, permission to represent Spain from the English king James I, who himself was seeking greater absolutism in his own state.
It is sometimes said that Gentili and his predecessors, described in this chapter, were not discussing international law at all but were merely continuing the rich medieval genre of books about the laws of war. This seems to me to miss a profound point. The State is defined by law and by war: it is the State's monopoly on legitimate violence, within and without, that marks it as a State. Once a society of states comes into being, the laws of that society are perforce about war, just as the laws of a single state are about keeping the civil peace.
During Gentili's last years as an advocate, he was called upon to comment on whether there should be common-law judges sitting on appeals from the English Court of Admiralty. As one would expect of the former Regius Professor of Civil Law, Gentili wished to have the appeals bench consist solely of civil lawyers. The English common law, he argued, was not suited to lawsuits involving foreigners, whereas all parties would be perfectly satisfied “to be judged according to the ius gentium as found in the civil law.” The king need only require the appellate judges to administer “the English civil law.” This step—which makes international law the law of the sovereign, the “law of the land”—is no mere extension of feudal authority, but rather represents a journey to a new world. The State, only recently objectified, is now demanding recognition for itself and its counterparts. It is demanding recognition for an entire society of states.