Ius Commune

From Max-EuP 2012

by Nils Jansen

1. The idea of a European common law

The concept of ius commune designates the ‘European common law’ (gesamteuropäisches Gemeinrecht, Wieacker) and thus the common object of the learned European legal discourse in the time between the 12th and the 19th centuries. For modern lawyers, this idea of a legal discourse being independent of the actual rules that are applied before the local courts is difficult to understand. It is hardly surprising, therefore, that there are few concepts in the field of European legal history that are more unclear and more disputed than this one. This is not only so because the discussion has often suffered from idealistic assumptions with regard to European legal history and to the future of European private law. Perhaps more importantly, the meaning of ius commune has always been complex; in addition, the historical concept is difficult to describe on the basis of modern concepts of law that are closely connected with the concepts of legal validity, on the one hand, and the state, on the other. The concept of the ius commune, however, lacked both these aspects.

Ius commune or ‘common law’ was the law that was common for all citizens or human beings; its counter-concept being ius proprium, ie the statutory law of a town, a local custom, the law of a region or the privileges of individual Princes, towns, or groups of population. If this conceptual contrast is considered from the practical perspective of a lawyer asking which legal rule to apply in a particular case (and that was usually a basic question in legal proceedings), the ius commune was characterized by its subsidiary applicability. If there was some specific local rule of law, this rule usually had to be applied rather than the ius commune. It is easy to see, however, that such a kind of common law need not be universal; rather, there could also exist regional ‘relative’ common laws, such as the common laws of England and Scotland, or Saxon or Swabian law in those areas, where the Saxon Mirror (Sachsenspiegel) or the Swabian Mirror (Schwabenspiegel) were applied. Thus, when the French nation emerged, the King’s national law was often contrasted as the new ‘common law’ with the local customs and statutes.

In contrast to those local, ‘relative’ common laws, the Roman-canon ius commune (see 2. below) was a specifically European and thus universal common law. This becomes apparent from the fact that European jurists did not usually ask, in which sense and for which reasons this ius commune and its Roman textual foundations could be good law. Of course, there are arguments justifying the applicability of Roman law; these are, first of all, the idea of a translatio imperii, according to which the ancient Roman Empire’s domination of Christianity had been succeeded by the Holy Roman Empire. A comparable argument was later the so-called Lotharian legend, according to which the use of the Digest had been prescribed in 1135 by the Emperor Lothar III of Supplinburg. But such arguments—and also their later refutation by Hermann Conring—were not part of the legal but rather of the political discourse. They found no place in the leading legal text books. From the legal perspective of learned lawyers, the question as to the validity of the Roman texts of the Corpus Juris Civilis apparently needed no answer. The ius commune was based on the self-referential practice of legal science, which had achieved a high degree of autonomy from the political process. In this context, Roman law was seen as an expression of legal rationality; there was no doubt about its being a universal grammar of the law. This was the reason why it also had to be considered when applying a ius proprium. The conceptual tools and the intellectual categories of the law could only be found in the context of Roman law; and, thus, they were also decisive for applying and discussing local rules. Hence, the ‘validity’ of the ius commune and the ‘validity’ of the ius proprium were wholly different matters: local law was based on the political command of a Prince, on the traditional custom of a local community, or on the legislation of an autonomous city. The ius commune in contrast represented the rationality and justice of the law, its principles being binding imperio rationis rather than ratione imperii.

2. The elements of the Roman-Canon ius commune

The Roman-canon ius commune was based on a range of different legal sources, and it integrated two independent legal systems, namely the secular Roman law, on the one hand, and the canon law of the Catholic Church, on the other hand.

The core of the ius commune had always been the Corpus Juris Civilis. In substance, the Corpus Juris of the ius commune was mainly a ‘critical’ edition of Justinian’s legislation, which had been slightly re-ordered; yet, at the beginning of the 13th century, the Codex had been supplemented with the originally Lombard Libri Feudorum, which were the main source for the practically important feudal law. From the 12th century onwards, these Roman legal texts had again become the object of academic education at the University of Bologna; they became the foundation of a learned jurisprudence and hence quickly achieved a high degree of authority. This is confirmed by the many thousands of written manuscripts of the Corpus Juris, which must have been rather expensive for their owners even if they were not expensively decorated: one copy of the Corpus Juris consisted of several volumes, and, for each volume, the skins of about 100 sheep were needed; it would take three years for a good writer to copy the text of the Digest.

Alongside the Corpus Juris Civilis, the ius commune had from early on also embraced authoritative legal texts of the Catholic Church. The individual norms of the Roman Church had long been developed independently of one another; yet, at the beginning of the 12th century, they were compiled into a coherent law book, the Concordantia discordantium canonum. This text, which is better known under its later title Decretum Gratiani, was soon taught at the Italian universities; within a few years, it was generally recognized as the central textual basis of canon law. In the following centuries it was again and again supplemented with further collections of Papal legislation; later all these texts together became the Corpus Juris Canonici. Thus, the ius commune consisted of two independent bodies of law, which—despite being intellectually connected—often embraced conflicting values. From early on, the tensions resulting therefrom helped the learned lawyers to develop the law in a constructive way.

From the 13th century onwards, the ius-commune legal science became an increasingly independent element of the ius commune. Although always following an exegetical method, the learned lawyers had assumed an increasingly productive, innovative function in the medieval legal system. Main works, first of all the standardized Glosses (commentaries) to the Corpus Juris Civilis and the Decretum Gratiani, achieved quasi-legal authority, and during the following centuries this body of learned law was enriched with the work of authors such as Bartolus and Baldus. The medieval procedural law, which was mainly developed on the basis of canon law (Roman-canon legal procedure), and the doctrines guiding the application of conflicting texts of legal authority (theory of statutes) were altogether developed by those learned lawyers.

3. Application of the law

The ius commune had always been a body of law competing with particular local norms. Hence, its function and significance cannot be understood without considering the ius-commune doctrines guiding the application of colliding norms and conflicting texts of legal authority. These doctrines were based on the ‘theory of statutes’ which had been developed, during the 13th and 14th centuries, in the context of the political circumstances in upper Italy. According to this theory, the law of the many city-states was granted priority in the application of the law; yet, at the same time, the dominance of Roman law was ensured first by the maxim of interpreting the political legislation narrowly (statuta sunt stricte interpretanda) and secondly by a presumption favouring the application of Roman law (fundata intentio). As a result, it was often assumed that unwritten law could not be applied by a court unless it had been proven by the party alleging the norm in question. Yet, those principles favouring the use of Roman law were probably not only an expression of legal elites attempting to control the administration of the law, but likewise rested on a conviction of the intrinsic reasonableness and superiority of the Roman rules.

Even if these doctrines appear clear as a matter of legal theory, their actual significance for the practice before the courts is more difficult to estimate, as this practice presents a complex and diffuse picture. Thus, it was apparently possible, at least in Italy, to apply a statute by means of analogy if this statute was not contrary to a legal principle of the ius commune. In Germany, further problems resulted from an even more complex mixture of municipal and regional legislation, individual privileges, and written and unwritten custom. From the 17th century onwards, it therefore became increasingly difficult to draw a clear line between written and unwritten law, as custom could be regarded as unwritten law even though it had been restated in a document. In addition, it was disputed whether the fundata intentio presumed a proof of the actual reception of the Roman rule in question. In later times solutions to such complex questions were found less on the basis of a decision about which rule to apply, rather than on the basis of a Romanist interpretation of the particular laws: differences between the ius commune and the local law vanished when the local rule was interpreted in the light of the principles that could be found in the learned literature of the ius commune.

4. Ius commune and European legal history

It would be wrong to assume that the ius commune was ever historically or regionally invariant. During the 13th and 14th centuries, it was limited to what is today Italy, southern France and the Iberian Peninsula; here its success was based on the rationality and the professionalism of learned lawyers, who had been taught on the basis of Roman law, and on the persuasive force of the opinions which those lawyers wrote on the basis of predominantly Roman sources. After the reception of the ius commune in Germany, Roman law even enjoyed institutional support. In the Reichskammergerichtsordung of 1495/1555 (the statute concerning the Reichskammergericht (Imperial Chamber Court)), it was explicitly laid down that its judges had to apply the ‘common laws’ (gemeine Rechte), ie the canon and Roman law. In contrast, the use of Roman law was restrained in other countries, especially in France, when these countries developed a national identity and the legal profession accordingly favoured the application of local law.

Nevertheless, even in France the ius commune remained the main subject of legal education at the universities and the main object of the learned discussion of private law. Although leading humanist writers (humanism) in France had historicized Roman law, it continued to be seen as the universal grammar of the law. None the less, from the 17th century onwards, the applicability of the Roman sources became more and more a problem also in other European countries. This practice had originally found its justification only in the learned ius commune discourse. Yet, learned lawyers had also begun to explain and analyse the particular laws in an academic, learned fashion; famous examples were Benedict Carpzov, Iurisprudentia Romano Saxonica secundem ordinem Constitutionum D. Augusti Electoris Saxoniae (1638) or David Mevius, Commentarii in Jus Lubecense (1642–3). As a result of this new approach, the question of the actual reception of the Roman rules in legal practice became a central object of the discussions of learned lawyers and a vehicle for the further development of the law; see Simon van Groenewegen, Tractatus de legibus abrogatis et inusitatis (1649). In the second half of the 17th century, works were published that supplemented the presentation and explanation of the learned (Roman) law with a detailed analysis of the actual practice of the courts; examples are Georg Adam Struve, Jurisprudentia romano-germanica forensis (1670), Samuel Stryk, Usus modernus Pandectarum (1690–1712), or Johannes Voet, Commentarius ad Pandectas (1698–1704). Thus, the focus of academics shifted to the law as it was actually applied by the courts. In those works, Roman law was only one—even if central—element of the positive law.

It was a natural consequence of this development that the formerly uniform European ius commune came to be replaced by a range of different national ius-commune legal systems, such as the ius romano-saxonicum, the ius romano-germanicum, the ius romano-hispanicum, the ius romano-neapolitanum, the ius sveco-romanum in Denmark, and the Rooms Hollands Regt in the Netherlands. From the point of view of learned lawyers, though, those legal systems remained closely connected in their common relation to the Roman sources. All over Europe, the students were taught during the first year on the basis of Justinian’s Institutes; hence textbooks such as Vinnius, In quattuor libros Institutionum Imperialium Commentarius (1642) or Heineccius, Elementa iuris civilis secundum ordinem Institutionum (1725) were used throughout Europe. Furthermore, even the national or local laws were often presented in the form of ‘Institutes-textbooks’ (Institutionenlehrbücher), which explained the local laws by means of a comparison with the Roman Institutes of Justinian. Thus European legal science retained its common doctrinal learning that was based on the common tradition of the ius commune; this common learning offered an overarching intellectual and doctrinal framework for the increasingly different European systems of private law.

Starting in the 17th century, European universities supplemented the teaching of the Roman-canon common law with a scientific natural law. This tradition was represented by authors such as Grotius, Pufendorf, Thomasius and Christian Wolff, who continued with their work the earlier Thomistic natural law tradition of the late scholasticism in the spirit of enlightenment. In substance, this modern natural law mainly presented a strongly systematizing and modernizing reconstruction of Roman and canon law; conversely, the natural law became an important factor influencing the theoretical development of the ius commune and inspiring the national codification movement (codification). Thus the natural law became an additional element of the ius-commune tradition of European private law; this corresponds with the understanding prevailing in the 18th century (see I, 2, §§ 4, 12 CMBC).

5. Ius commune and common law

The relationship between the Anglo-American common law and the ius commune has long been the object of contention. During the last decades, the notion of the common law having developed independently (‘isolation of English law’, John H Baker) has successfully been challenged. Indeed, since the 13th century (Bracton), Roman-law, canon-law and later Natural-law authors have frequently influenced the common law’s development in important respects. In England and Scotland, too, the Roman ius commune was the main object of academic legal education (which was, however, dispensable for common lawyers). If the ius commune is characterized as a learned discourse overarching different legal systems, rather than a body of law of subsidiary applicability, the English common law should therefore be seen as a distant family member of the common European tradition of the ius commune.

6. Ius commune and European private law

During the 19th and 20th centuries, the ius-commune discourse has broken down as a result of the development of nation states, the codification-movement (codification), and the European political conflicts. However, during the 20th century, a common European legal science (European private law) has re-emerged. This development has been related by some authors to the tradition of the former ius-commune. However, the present European legal science lacks at least three essential characteristics of the traditional ius commune, ie a common academic language (Latin), common texts of reference (especially the Corpora Juris Civilis (Corpus Juris Civilis) and Canonici and the corresponding books of authority), and, above all, a certain degree of autonomy of legal science vis-à-vis the law applied in the practice of the courts.


Francesco Calasso, Introduzione al diritto comune (1951); Paul Koschaker, Europa und das römische Recht (4th edn, 1966); Helmut Coing, Europäisches Privatrecht (1985/1989); Tony Weir (tr), Franz Wieacker, A History of Private Law in Europe (1995); Lydia G Cochrane (tr), Manlio Bellomo, The Common Legal Past of Europe, 1000–1800 (1995); Klaus Luig, Römisches Recht, Naturrecht, nationales Recht (1998); Reinhard Zimmermann, ‘Europa und das römische Recht’ (2000) 200 AcP 243; Peter Oestmann, Rechtsvielfalt vor Gericht (2002); H Patrick Glenn, On Common Laws (2005); Nils Jansen, The Making of Legal Authority. Non-legislative Codifications in Historical and Comparative Perspective (2010) ch 1.

Retrieved from Ius Commune – Max-EuP 2012 on 27 January 2022.

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