Fantasy Aztecs in the future. So there's a fantasy Mexico in the Forgotten Realms, it seems - full of scorpion men, jaguar men, Yuan-ti, and the rest. It's called Maztica. Fast forward 2,000 years. Now all the scorpion men, jaguar men, Yuan-ti and the rest are putting cybernetic implants in their bodies, riding around in driver-less cars, smoking e-cigarettes, and getting tattoos. The PCs are private investigators solving murders: there is a separate police force and legal system for each of the different races, and the PCs have to work in a fashion hidden from the authorities.
I got thinking about this today. I'm not really sure where I was going with the idea of PCs being private investigators solving murders, but I like it, so let's pursue it.
Future Maztica is a legal pluralist society: there are different legal systems for different populations. Early medieval Europe was a bit like this. You had secular and ecclesiastical courts, the separate lex mercatoria followed by merchants; local customary law which varied from region to region and often from village to village; the general Germanic customary code; the revived Roman Law used in universities; royal courts and manorial courts and guild courts. A colleague of mine studies the history of law as represented in art; she once showed me photos of an old guild court in Florence which was the court used by the wool merchants' guild. It had its own rules, judges and punishments completely separate to those used in the city proper.
Colonial empires were also often a bit like this. In most of the British Empire, for instance, if you were, say, an English merchant, your commercial transactions would be covered by English contract law. If you killed a native, you would be subject to English criminal law. But the native populations were often left to their own devices and their own pre-existing legal systems. The Ottoman Empire even signed treaties, known as "capitulations", with European powers, by which citizens of those states within the empire would be subject to their own law, not that of the Ottomans.
Legal pluralism is interesting because it is fraught with issues of power. The reason the church had its own ecclesiastical courts in renaissance England was because it had the power to do so. (These courts still exist, in fact, although in a much diminished capacity.) One of the reasons why there was a competing Court of Chancery in England, separate from the courts of common law until the late 19th century, was because it originated as the king's court. The reason why there were separate legal systems in colonial empires was because those systems were imposed from without. And so on.
Future Maztica is like that. Scorpion-men, tabaxi and yuan-ti are all powerful. More powerful than humans. Why would they abide by human laws? They are in a position like the British authorities in India; the humans are like the native population of India who were left to their own devices - unless they bothered somebody British. So the only time a human in future Maztica interacts with the legal systems of the scorpion-men or yuan-ti is when he or she is accused of a crime against one, or is involved in a dispute with one.
So the PCs are in a tough position. They are trying to solve crimes. But whenever they do, they come against really unspeakably difficult and alien legal provisions with (to the human eye) completely unrealistic demands.
For example: a mother comes to the PCs. Her son was killed by a yuan-ti. She wants the matter investigated. The yuan-ti police don't want to know. Moreover, in the yuan-ti criminal justice system, the only evidence admissible in court is that obtained through confession, and then recorded psionically in the brain of an observer, who is then called as a witness. And this witness has to be a yuan-ti of a certain type. So the PCs have to: a) find out who the yuan-ti was who killed the woman's son; b) try to get that yuan-ti to confess; c) try to find another yuan-ti of the certain type which can act as a witness in court; d) get that yuan-ti to agree to psionically record the confession and then appear in court; and e) convince the yuan-ti police to take the matter seriously.
Perhaps this works better as the plot of some sort of pulp fantasy novel than a game. The simpler option is: it's basically like Cyberpunk 2020. The PCs are criminals and rogues, or some of the other Cyberpunk 2020 style careers (journalists, medics, etc.), and they have to operate in a society in which human beings are very much at the bottom of the pile. Humans live in the criminal underbelly of future Maztica, and if they are caught doing anything which even comes within a mile of harming the interests of a scorpion-man, tabaxi, or yuan-ti, they come under the power of the police of that race and its harsh and incomprehensible laws. They're not so much "victims of the new" as "victims of the powerful monsters which run the show". Yet since it's the scorpion-men, tabaxi and yuan-ti who have all the money...what's an enterprising human criminal to do?