In the October issue of the American Historical Review (before this blog existed...), there were a couple of pieces of interest to legal historians, including, Ralph Mathison, Peregrini, Barbari, and Cives Romani: Concepts of Citizenship and the Legal Identity of Barbarians in the Later Roman Empire. Mathison argues, in part:
"The ancient world, and in particular the later Roman Empire, can provide us with a laboratory for investigating what does and does not work in dealing with the interlocking issues of citizenship, ethnicity, and identity. It permits us to inform our understanding of emotionally charged phenomena from a more distanced and objective perspective. The concepts of cosmopolitanism and world citizenship go back at least to Hellenistic philosophies of the fourth and third centuries b.c.e. The Cynic Diogenes, for example, stated that he was "a cosmopolite": "a citizen of the world." The Stoics believed that the whole world constituted the only true city, whose citizens were of necessity "good" people. In the Roman Empire, in the early second century c.e., the Stoic philosopher Epictetus likewise spoke of being a "citizen of the world." Even the philosopher-emperor Marcus Aurelius (161–180) called himself a "citizen of the world-city," opining that "under its laws equal treatment is meted out to all." ...A close examination of the evidence...challenges the prevailing opinion and suggests that concepts of citizenship, from the personal, legal, and metaphorical perspectives, continued to play a vital role in defining personal and legal identity after 212 c.e. In particular, Roman citizenship continued not only to be a factor in how people perceived themselves, but also to entail legal rights that were available only to persons who were identified as "Roman citizens."
For the rest, go here.