Moral Code is a function of the Law. Period. And is just as much of a fiction as the law itself.
But that doesn't mean either one are illegitimate.
The Legitimacy of the US government does not rest in our consent but in its ability to defend itself, the fealty of its soldiers to the fiction of the rule of law rather than a Monarch and its recognition of and by other nations who do business with it as a sovereign entity. Otherwise the Native Americans have the legitimacy of government as the original occupiers. But the world's other recognized sovereigns - recognize the US Republic as the Legitimate Sovereign Jurisdiction over the lands it claims.
Research "Conquest" in Black's Law and International Law.