Gentili's Ius Post Bellum and Early-Modern Peace Treaties

Abstract

To Gentili falls the merit of having made the ius ad bellum a logical third part of the laws of war, after the ius ad bellum and the ius in bello. After him, most treatises on the laws of war or later, on the laws of nations, included some reflection on the subject, although few as extensive as Gentili. The integration of the ius post bellum into the laws of war caused Gentili’s concept of peace to be determined by his concept of war. It was this and the modernity of his concept of war that made for the novelty of Gentili’s doctrine of peace. Gentili broke away from the classical just war doctrine with its view of war as a unilateral instrument of justice. Building on notions from medieval and humanist civil jurisprudence, he defined war as a contest for victory between equal parties. Absent the possibility to decide who had justice on his side, war was degraded from an instrument of justice to an instrument of law enforcement through victory, without any guarantee that victory would be delivered to the just side. Victory bestowed upon the victor the right to enforce his claims and dictate the terms of peace. If there was no clear victor, then war had failed its purpose. Peace through agreement was thus a solution by double default, through the failure of man to discern justice, and through the failure of achieving victory.All this brought Gentili to distinguish two bodies of laws, which together made up the ius post bellum: the ius victoriae and the ius ad pacem. This scheme of things allowed Gentili to grant legal force to all the victor or the consent of the treaty partners decided. In this sense, Gentili gave a legal basis to the practices of the European States without – the ius victoriae – and within – the ius ad pacem – Europe. But Gentili was no positivist or consensualist. Rather than describing all the particular practices of States in making peace, he defined the general rules they ought to apply in making peace. Here he brought justice back into the equation, for its own sake as well as for the sake of making peace stable and sustainable. However, the logic of justice was more dominant in his ius victoriae than in his ius ad pacem. This is unsurprising. Under Gentili’s system, peace through agreement was one step further removed from the ideal workings of justice than peace through victory. As such, his conception of peacemaking through treaties came close to reflecting the intra-European practices of his day and age. But to some extent, Gentili also failed to grasp the current of events. Compared to the solution of the neo-scholastics, his system represented the path not taken. By distinguishing between objective and subjective justice, the neo-scholastics offered another way out of the dilemma of justice and sovereignty. Whereas in Gentili’s work, there was only one legal order and one concept of war wherein legality and justice worked together, the neo-scholastic demarche inspired another approach: that of distinguishing two separate spheres of law – that of internal and of external law, that of the natural and the positive law of nations – and two concepts of war, just war and legal war, or solemn war in the words of Grotius. It was Grotius who laid out this scheme but it took Wolff and Vattel fully to consummate it in their dual system of the necessary and the voluntary law of nations, of just war and war in due form, of just peace and peace in due form. The dualistic outlay of the system, Grotius took from the neo-scholastic tradition, but for the concept of solemn war and for his doctrine of peace treaties, Grotius took inspiration of the civilian tradition and from its two foremost, recent representatives, Ayala and Gentili. The success of the dualistic approach to war and peace can, at least in part, is explained from the fact that it answered to the practices of States in Early Modern Europe. When making war – in their declarations and manifestos of war, in their alliance treaties –, States continued to operate the language of the just war, and particular the classical just war doctrine. When making peace, all this was forgotten as States turned to the logic of solemn war, or to the Gentilian logic of war as a contest between equal parties.