Bartolus of Sassoferrato, the leading jurist of his day, whose influence spanned several centuries, first formulated an equation of family and its property (substantia) that cast an image of family enduring over time in the immediate passage of property from father to son. That tie was so pivotal that a son could be termed, however incorrectly in strict legal terms, as a co-owner of the estate with his father. Disinheritance was difficult to conceive of in these terms, although it was an allowed legal institution. Subsequent jurists followed Bartolus's lead, even though they were likely to face only situations where the paradigmatic passage of haereditas from father to son was not possible.

Modern legal systems are by and large very similar across most countries on earth. A widespread opinion ascribes this similarity to common heritage from Roman law, because this law (as codified under the Roman emperor Justinian 529–34 CE) was so useful. This is not, however, fully correct. Countries living under law originating in Europe share the same methods of legal argumentation, share many principles and categories, and also have a vast mass of procedural rules and substantive law in common. That conformity, however, did not come about by directly adopting legal rules or doctrines from Justinian. Instead, Christians all over Europe lived under the learned canon law of the Roman Church, whose lawyers from the late twelfth century adopted doctrines of medieval Roman law whenever there existed no appropriate ecclesiastic rules. Roman law regained importance in the Middle Ages through canon law; this is why Roman doctrines so often still survive.

Ideas and practices often perceived as modern carry a complex premodern history that cannot be excised from their present. This is certainly the case of trade embargoes as economic means for the attainment of political goals. For a variety of reasons, however, tracing change over long periods of time remains an exercise in chronological and spatial jurisdiction. Further complicating our understanding of the convoluted relationship between past and present has been the increasingly pronounced tendency to write in the vein either of a “history of ideology” or, conversely, of a “history of action.” In fact, “theory” and “practice” existed in a dialectical relationship, a cyclical tug of war that produced not so much winners and losers as complex realities that require a thick reading of legal, political, cultural, and social change. This chapter, by contrast, seeks to explain the transfiguration of the legal tradition from the perspective of international law history by focusing on two interrelated transitions.

Throughout the Commentaries, Blackstone repeatedly availed himself of comparative legal history. Comparison allowed him to detect the invariable principles of legal experience and organise his systematic exposition of English law around them. This method proved crucial in Blackstone’s treatment of custom, as it allowed him to present the chief source of English common law by addressing the main questions concerning the nature of custom that had been raised earlier by Western jurisprudence. The paper will explore the depth of Blackstone’s engagement with such traditions. In doing so, it will investigate whether custom was understood differently on the two sides of the Channel.

Jean de Blanot, the enigmatic Iacobus Aurelianus, and Jean Blanc de Marseille are the first known French lawyers trained in Italy to have shown interest in one of the most famous custumals in medieval Europe, the Lombard book of fiefs known by the name of Libri Feudorum. Considering that this compilation was increasingly gaining authority in the Italian law schools, this chapter shows how these three lawyers re-elaborated these teachings and compared (or opposed) them to local bodies of norms. By observing how they developed different notions of custom and argued about the validity of the Libri Feudorum outside Lombardy, the chapter unveils the problematic dialectics between Civil law, local custom, and practice, and provides some insights into the making of the ius commune, its practical and historical roots, its geographical dimensions.

This chapter explores Shakespeare’s knowledge and use of the European ius commune. The ius commune was the amalgam of Roman and canon law taught in Europe’s universities, including England’s, and employed as the basic source of law in European legal tribunals to the eighteenth century. It was applied in the courts of the English church, the Admiralty, the universities, and some of the courts of equity that had come to life in the sixteenth century. These courts were served by a separate legal profession, the English civilians. Recent interest in Shakespeare’s knowledge and use of law takes virtually no notice of this aspect of English law. This chapter demonstrates a number of points. The first is that Shakespeare was familiar with the ius commune. He used its terminology and then made something of it in the dialogue of his plays. The second is that this knowledge had results in their thematic coverage. He employed his knowledge of the ius commune to shape and enrich the substance of the plays. The third is that his use of the civil and canon laws was connected with areas of contemporary controversy in England.

The Court of Chivalry enjoyed a high political profile, owing to the military nature of the suits and the high social status of its litigants. Within the context of long periods of warfare during the fourteenth and fifteenth centuries, the Court maintained its reputation on account of nobles and knights wishing to challenge the legitimacy of perceived rights to lucrative ransoms of prisoners or to bear heraldic coats of arms. The procedures employed were predominantly those of the continental ius commune rather than the common law, probably on account of the international body of customs and practices found in the 'law and custom of arms' which underpinned the legal principles applied in the Court. In addition to its eclectic jurisdiction, the networks and connections of the legal personnel helped shape its distinct identity. The Court formed a nexus where highly qualified men from other courts and administrative traditions pooled their considerable intellectual understanding and practical experience. They were often educated in civil and/or canon law, but were probably both respected and well-placed from their involvement in parliament and other diplomatic and judicial business to act as commissioners and advocates in the often highly charged political circumstances of Court of Chivalry cases.

The concept of equity is often assimilated with that of Aristotelian epieikeia, a process that corrects rules when their application to a certain case would be unjust or contrary to the intention of the legislator. In the middle ages - while theologians had written at length on the concept of epieikeia - glossators, commentators, and canonists adopted a concept of aequitas completely unrelated to it. This barrier between law and theology lasted throughout the medieval period. By the mid-sixteenth century the concept of epieikeia had become familiar to legal writers and, through the work of humanist jurists, was explicitly associated with aequitas. The introduction of epieikeia in legal scholarship opened the door to the influence of scholastic theology over the concept of equity, as lawyers and theologians worked together to build a novel concept of aequitas/epieikeia as judicial power to interpret law beyond its letter.