In his essay On Duties, Cicero distinguishes between statute or civil law and 'the moral law which nature itself has ordained':
As I have said before - and it needs constant repetition! - there is a bond of community that links every man in the world with every other. Though this bond is universal in application, it is particularly strong as a unifying link between people of the same race: between actual compatriots the link is closer still.
The existence of this natural bond of community between all human beings explains why our ancestors chose to make a distinction between the civil law of the land and the universal law. The law of the land, it is true, ought to be capable of inclusion within the universal law, but they are not synonymous since the latter is more comprehensive.Cicero regularly refers to this universal law as 'natural', and so one thinks of principles of natural justice, and of natural law, which dates back to Roman law. The idea of a bond of community between all humans surely contains the germ of the concept of universal human rights [and universal human responsibilities], in spite of the rigidly hierarchical nature of Roman society, the overall powerlessness of women, and of course the general acceptance of slavery [upon which much of the economy was based]. Cicero doesn't take the concept too far, taking human nature as 'god given', the god he mentions being Jupiter. His claim that 'people of the same race' have a stronger bond, and compatriots a stronger one still is both questionable and a commonplace. David Hume would certainly have agreed, and it's a bit reminiscent of Singer's 'expanding circle', though I've often wondered myself about the strength of the nationalist bond, a very weak bond in my case. I'm not sure what he means by 'people of the same race', as opposed to compatriots, and I'm not at all sure if his contemporaries understood it either. The Romans at this time were forever fighting peoples on their borders - in fact this sort of fighting went on throughout the many centuries of Roman power, and presumably they considered these 'barbarian' peoples as races rather than nations. Then again, they may have distinguished some of their enemies as more civilized than others, as 'compatriots' among themselves. In any case Cicero was clearly grappling with the same sorts of issues around the extent of human sympathies that philosophers and psychologists have been grappling with in more recent times, and which genetics and evolutionary psychology have been helping to shed light on - even as they have rendered the concept of race redundant.
The main subject of Cicero's essay, though, is the relationship between 'right' [as in doing what is right] and 'advantage' [as in self-interest]. He treats the subject confusingly at times, and I might look more closely at it later.