Illustration of the Sack of Rome by the Visigoths.
During the Sack of Rome in 410 AD by the Visigoths, liturgical vessels are brought to safety in a church. It was the beginning of the decline of Roman power and of great migratory movements. © Wikimedia

Looking back at the Roman Empire from today's perspective, one would expect a majority of the population to have had Roman citizenship. Surprisingly, however, this was not the case until 212 AD. “Only about twenty to thirty percent of the population were considered full citizens, citizens of the great Imperium Romanum. The rest were 'merely' citizens of a city within the Roman Empire, such as Athens or Alexandria. Regional and local autonomy was acknowledged and encouraged during the Roman Empire,” explains Johannes Michael Rainer, a law scholar at Paris Lodron University in Salzburg who focuses on Roman law and modern private law. In addition to Roman citizenship, the Roman Empire also acknowledged membership of a province, which was, however, less significant in legal terms than the citizenship rights of the city in which one lived. The latter involved important political rights. If, in special cases, members of the Athenian upper class were granted Roman citizenship in addition to citizenship of the city, their rights as Athenians were not lost. “In our research project we are now exploring this multiple citizenship. It is exciting to note that in 212 AD, all inhabitants of the Roman Empire were granted Roman citizenship by dint of the law, without any precondition. While they remained citizens of their city, this status increasingly lost importance,” Rainer explains.

Focus on the legal system

In the context of this interdisciplinary research project, which is funded by the Austrian Science Fund FWF, Rainer is the first to study the phenomenon of enormous immigration from a legal perspective. Especially in the 4th century AD, the “century of migration”, the European continent was confronted with a new and unusual level of immigration, probably numbering in the millions. Based on historical sources, researchers even assume that the migration rate then was disproportionately higher than today. Then as now, the phenomenon confronted the state with new and comprehensive challenges. After all, civil rights issues affected the long-established population and newcomers alike. The focus on rights raises several questions: what was the legal situation of foreigners as compared to Romans? What measures were taken to deal with migrants? What were the strengths or weaknesses of the system? “We want to vet the models of the past for their usefulness for the present day and thus contribute to solutions for current challenges presented by migration. For this purpose, we are cooperating with a number of universities from all over Europe and from the USA and also with the European Commission,” Rainer reports.

Map that shows migratory movements in the Roman Empire of the second to fifth centuries.
Migratory movements in the Roman Empire of the second to fifth centuries. © Novarte, CC BY-SA 4.0

Foreigners and Romans equal before the law

A deterioration of the climate was probably the central factor that induced entire peoples to migrate from their regions to the west. A massive drop in temperatures resulted in crop failures and endangered the livelihood of many people. “One essential difference between ancient migration flows and modern migration is the fact that men did not leave on their own, but took their wives and children along. The migrant groups of that time therefore reflected the entire spectrum of the population,” Rainer explains. The Latin legal term peregrinus (foreigner) therefore applied equally to men, their wives and their children. The political leaders had long been reflecting on the sort of rights these foreigners should enjoy in the Roman Empire and how they would be enforced. “It is very interesting to note that as early as in the Roman Republic, probably at the beginning of the 3rd century BC, a separate, non-partisan and independent jurisdiction was established for foreigners. The praetor peregrinus or minister of justice who presided over this institution was exclusively responsible for foreigners and had to ensure that private law accorded them the same rights as Roman citizens,” Rainer emphasises. In practice, this meant that a legal dispute between a Roman citizen and a Germanic merchant in Rome, for example, required equal treatment for both. This full equality applied to private law, but, as Rainer notes, criminal law provided for hardly any differences either.

Too little know-how and too much trying to keeping people out

The Roman Empire knew a diverse range of measures to cope with the massive immigration – ranging from fending them off and erecting borders to integration, to having people settle as farmers, or enrolling them in the Roman army. Moreover, the remains of the limes still testify to the enormous dimensions of the border fortifications. In order to better understand the overall situation, the political situation and the measures taken, the researchers rely on a wide variety of source material. In addition to legal sources, such as Emperor Justinian's collection of laws from the 6th century AD, they also analyse literary sources written by contemporary intellectuals and political reports. In spite of equality before the law, there were many problems and open questions in dealing with the numerous refugees. “From the very beginning, those in charge relied far too heavily on keeping people out instead of investing more in meaningful integration measures. In addition to the lack of experience, there were also decades of oscillating between open and closed borders,” Rainer says, summarising some of the central reasons for why integration failed to be successful. Moreover, in 378 the effort to expel immigrants who were already integrated culminated in an armed conflict that led to a defeat of the Romans. For Rainer, this constitutes an example of failed integration policy.

Foreigners were able to flourish

Other aspects, however, worked really well. Rainer considers the high degree of social permeability, not only in the military service, to have been a vital strength of the system: “As a foreigner, you could rise to the upper class comparatively quickly. We have seen cases in the 4th and 5th centuries AD, for example, where a second-generation migrant of Germanic origin rose to the position of prime minister.” An essential prerequisite for such a career was mastering Latin, the official language. From today's point of view, the voluntary conversion to the official religion of the Roman state, Christianity, was another relevant step for the immigrants towards social and educational integration. As far as the state as a whole is concerned, other positive factors included the mutual rapprochement, the flexibility of the law, and consideration for the traditions and particularities of the migrants. Rainer is intrigued by the new models developed for the integration of foreigners by peoples who were themselves descended from immigrants and inherited their realm from the Romans. Roman law was used, for example, to reorganise the distribution of land or to increase taxes for large landowners to finance the army. It took this interdisciplinary approach with a special focus on the legal system to reveal the lessons to be learned from the past, not only for researchers but also for present-day Europe.

Personal details Johannes Michael Rainer is full professor of Roman law and modern private law at Paris Lodron University Salzburg. An interdisciplinary approach has marked his academic career from the outset. He played a key role in designing the Erasmus programme at several universities (Graz/Munich/Roma III) and inter alia initiated the Salzburg Summer School “European Private Law”. His research interests include Roman constitutional law, the history of Roman law up to the present day and European private law.


Rainer, J. Michael: Das Römische Recht in Europa, Manz Verlag Wien, 2. Auflage, 2020
Rainer, J. Michael: Minima sur la citoyenneté romaine, in: J. Bouineau (Hg.): L'environnement méditerranéen. De l'Antiquité vécue à l'Antiquité réinventée, Paris 2019