As I’m sure you’re all aware, today is “Martin Luther King Jr. Day”, MLK’s birthday. If you have not read it (or have not read it in a while), I strongly encourage you to peruse his “Letter from Birmingham Jail.” In it, he explains the important difference between “legal” and “just.” Though MLK does not explicitly mention the Stoics as an influence (as far as I know), you can see similar claims made by them (for example, the idea that “natural law” and “conscience” should hold primacy over one’s actions is often credited to the Stoics).
You can read “Letter from Birmingham Jail” here: https://www.africa.upenn.edu/Articles_Gen/Letter_Birmingham.html
You can listen to it here: https://shows.acast.com/words-matter/episodes/in-honor-of-dr-martin-luther-king-a-letter-from-birmingham-j
Here is a popular passage that resonates with me:
Injustice anywhere is a threat to justice everywhere. We are caught in an inescapable network of mutuality, tied in a single garment of destiny. Whatever affects one directly, affects all indirectly.
It reminds me of a passage from Marcus Aurelius:
Among reasonable creatures [logikon zôon], constitutions, friendships, households, and gatherings were found, conventions too and armistices in war. Among the yet higher, even among beings in a sense separated, there subsisted a unity such as obtains among the stars. Thus progress towards the higher was able to produce a sympathy [sumpatheia] even in what are separated.Meditations 9.9
All early Stoics from Zeno to Marcus Aurelius emphasized the objective fact that we are connected in at least three ways: first, as nodes in the cosmic web of cause-and-effect—what affects one part directly affects all other parts indirectly; second, as fellow citizens of socio-political communities whose destinies are bound together with the destiny of society as a whole; and, third, as fellow citizens of the cosmos, who are all responsive to universal reason and “natural law.”
MLK uses the important distinction between the second and third kind of ‘citizenship’ in his justifying certain tactics to his reader:
One may well ask: “How can you advocate breaking some laws and obeying others?” The answer lies in the fact that there are two types of laws: just and unjust. I would be the first to advocate obeying just laws. One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws. I would agree with St. Augustine that “an unjust law is no law at all.” […] A just law is a manmade code that squares with the moral law or the law of God. An unjust law is a code that is out of harmony with the moral law. To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust. All segregation statutes are unjust because segregation distorts the soul and damages the personality. It gives the segregator a false sense of superiority and the segregated a false sense of inferiority.
St. Augustine and St. Thomas Aquinas must have been inspired by Cicero:
Natural Law summons to duty by its commands, and averts from wrongdoing by its prohibitions. And it does not lay its commands or prohibitions upon good men in vain, though neither have any effect on the wicked. […] We cannot be freed from its obligations by senate or people, and we need not look outside ourselves for an expounder or interpreter of it. And there will not be different laws at Rome and at Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and all times, and there will be one master and ruler, that is, God, over us all, for he is the author of this law, its promulgator, and its enforcing judge. Whoever is disobedient is fleeing from himself and denying his human nature, and by reason of this very fact he will suffer the worst penalties, even if he escapes what is commonly considered punishment.De Res Publicā 3.22.23
Cicero himself was inspired by the Greek Stoics, among whom the idea of ‘common law’ (koinos nomos) in agreement with nature was first promoted. You can trace it all the way back to the “Hymn to Zeus” by Cleanthes. Here’s Diogenes Laertius that speaks to this:
[L]iving virtuously is equivalent to living in accordance with experience of the actual course of nature, as Chrysippus says in the first book of his “On Ends;” for our individual natures are parts of the nature of the whole universe. And this is why the end may be defined as life in accordance with nature, or, in other words, in accordance with our own human nature as well as that of the universe, a life in which we refrain from every action forbidden by the law common to all things [koinos nomos], that is to say, the right reason which pervades all things, and is identical with this Zeus, lord and ruler of all that is. And this very thing constitutes the virtue of the happy man and the smooth current of life, when all actions promote the harmony of the spirit dwelling in the individual man with the will of him who orders the universe.Lives of Eminent Philosophers 7.87-88
The relevant point here is that “the end” or “the goal” of life includes not acting against the ‘common law’ (a.k.a. ‘natural law’), regardless of whether it is the actual law of the land. So if there were self-acclaimed Stoics in 1960’s America, I would expect them to be actively against segregation and in support of the movement driven by Martin Luther King Jr.