This is irrational at best. Perhaps you are not particularly well-versed in the history of law, but it must be remembered that the very concept of jurisprudence in the strict Western canonical sense (e.g. a courtroom, judge, signed documents, "legally" parcelling land, etc.) has really only been practiced by governments derived from the teachings of the Western ideology.
The matter at-hand is not just a matter of removal of land, but forced acculturation, mass slaughter, and removal to some of the worst areas for agricultural and indigenous way of life possible (as well as removal from all oil and possible economic resources). It'd be really nice to separate the process, as you attempt to do in your original post, but unfortunately that is not possible, because what occurred is reasonably categorized under the nature of genocide.
It seems as though you infer that Natives have long had a practice of law and courtroom justice, but this was all directly conferred upon them upon the arrival of the European - a system that had absolutely nothing to do with their way of life, their values, virtues, or even economic interests. Consider it somewhat akin to the forced slavery of the Africans, they were picked up, bullied into an economic system that systemically left them at a significant disadvantage, and essentially herded into some of the most arid conditions on Earth, in the name of "legal precedence" that had not existed as such in their society previously.
Let's go ELI5 - if I enact a set of rules that allows me to displace you from your household and take it over myself (relegating you to my tiny shack), surely you would protest the decision? But it is of no worth, because the rules state that if I claim this as my house, it is, in fact my house. But is it my house, really? It'd be fair to say that you likely put in a lot of work on this house, perhaps developed it for your children, and theirs. But it is of no matter, because it is mine now, as per the rules. It'd be one thing if we had agreed on a set of rules, right? But we didn't, I created these rules and you bet your ass I created them to favor me in the process.
It might seem like an overt simplification, but that is essentially what happened. You have a very acculturated way of understanding these things. Looking at this through the lens of Western culture will yield no results. Why would it? If you're not trying to understand their point of view, how can you?
Look, I'm not advocating that we return the United States to its' ancestral inhabitants, it is not even possible in a utopian world - but there is no question in my mind that American claim to these lands is based on ethically compromised grounds, you should at the very least respect that much. You say that you do not encourage what happened to the Natives, and you say that people should be allowed to live where they want, but you ignore the fact that the governance and legal precedents you heed disallow exactly that. So the only way to live on another's land is to take it, if you are not welcomed into it, correct? Perhaps that applies to, hmm...resources, too (cough Middle Eastern/Indochinese wars and imperial coups of Chile, Guatamala, Brazil, Nicaragua, etc.)?
Your legal writings amount to little more than nothing than the word
mustard
And yet, they've historically been used in large part to justify invasion, pillaging, social stratification and bylaws, as well as the very genocide - cultural, economic, and physical - that you deem reprehensible.
Do you still believe that you have a legal right to this land? Because you do. Does that mean it's morally correct or a well-founded conclusion based upon human ethics? No, it doesn't. History is history. No one is really advocating for the whole of the States to be returned to the Natives, but being put on equal ground for a change may well be enough.