If one individual wrongs another we generally agree that if possible that wrong should be righted, i.e. that the harm done to the individual should be undone as much as possible, and that the guilty party should be deprived of any benefits that followed from that crime. For example, if I steal your TV, and later that fact is discovered, then it is clear that I should be forced to give your TV back to you, or buy you a new TV of equal value if that isn’t possible. And generally the longer the wrong goes unaddressed the more we need to do to repair that wrong, or so it would seem. If my theft of your TV has prevented you from watching your favorite shows for a week then not only do I need to give you your TV back, but I need to somehow compensate you for the fact that you missed your shows as well. Of course deciding what is fair is often hard, and sometimes it isn’t possible to put things right, but it is an ideal we strive for.
Things become more complicated when third parties become involved. Obviously in the case of past crimes I am interested in third parties who happen to benefit, by inheritance, from wrongdoings. I claim that such inheritors do not need to give up any advantages acquired by inheritance in this way. My reasoning on this issue primarily follows from the fact that it serves no purpose to punish people (by taking away whatever advantages they have gotten in this way) who haven’t actually done anything wrong themselves. Of course those who think they should have such gains be taken away might reason that allowing people to come into advantages in this way is unfair. If our parents both had $10 and my parent stole $5 from your parent, so that we were born with $5 and $15 respectively then it seems unfair to you that I get more to start with. But the same inequality could exist if my parent simply worked three times as hard as your parent. If one situation is unfair then so is the other, because in neither case did you or I do anything to merit the inequality. I am actually sympathetic to the claim that it is an inequality that should be addressed, but I think the inequality lies in the ability to come into advantages based on birth alone, and not where the inequality comes from. As long as we allow people to be unequal at birth then it makes no difference how those inequalities came about.
And we can extend this reasoning to cover third parties benefiting from wrongdoing in general (given that the third parties are actually third parties, and not accomplices). Suppose then that I steal your TV and sell it to someone else, or possibly give it away, and that the people who receive the TV have no idea that it is stolen. I would maintain that we can’t force these people to give it back to you. What we can do is punish the criminal, forcing them to compensate you with something of equal value even if it isn’t the TV itself. It is then up to you to get your TV back from the person it ended up with. The reasoning behind this is that, like inheritance, whether someone gives you a TV, or sells it to you at a cheap price, is a matter of luck. These third parties haven’t done anything wrong, and so by punishing them you are effectively punishing them for having good fortune. And that doesn’t really make sense. Punishment exists to discourage bad behavior. Do we really want to discourage people from buying things or from accepting gifts?
Using this kind of reasoning I would argue that modern US citizens aren’t obligated to give back the land their ancestors stole from the Native Americans. The people alive today are neither those who did the stealing nor those who were stolen from. And thus trying to “give back” the land would be another kind of theft. Of course there are some who would disagree, reasoning that individuals involved in the initial wrongdoing were not people but societies, that the white/protestant/Andrew Jackson society stole from the Cherokee/Creek/etc society, and that since these societies still exist it makes sense to return the ill-gotten gains of the first to the second. However, I think the analogy between societies and people when it comes to questions of ethics is an illegitimate one, a kind of category mistake. In this specific case where the analogy breaks down is with punishment; it doesn’t make sense to punish a society. The purpose of punishment is to discourage certain behavior. But societies cannot systematically be punished (although governments, specifically the people who compose them, might be), to the extent that the people living in them use that knowledge to guide their political decisions. If the US returned land to the Native Americans it would be a voluntary decision on its part, and would not serve to set an example for other nations. And of course another difference between the two scenarios is that Native Americans are free to become US citizens and thus enjoy the stolen land as much as anyone else.
Of course this doesn’t mean that the Native Americans might not have complaints about their current situation, or want their land back. And an important part of justice (note: not ethics and punishment, which is what we were concerned with previously) is reaching a state of affairs that all parties can bring themselves to accept. For example, some Native Americans might feel that the land in which they can govern themselves as independent nations isn’t suitable (remember, the Native Americans were often resettled in the least desirable places). And if both sides agree that it isn’t fair for them to be stuck in an area they don’t want to live in the government might buy land in other areas from the individuals who currently own it, and convert it into a reservation. Or, alternately, some Native Americans might want to secede from the union completely, which might also be agreeable to both parties. In any case, such matters are generally not settled by appeal to overarching principles, but by reaching compromises based on the desires of the parties involved, as are many matters of justice.