And what by what mechanism allowed by Reason is it possible to appeal to a court higher than a Supreme Court? And, if we shall not have a Supreme Court, who gets the final say on the interpretation of law? State legislators? Congress? American republicanism is founded on the notion that individual liberty is more precious than majority rule. Thank God we have a Supreme Court which can protect individual liberty even when it is unpopular.

Does the Constitution give the Supreme Court the final say over interpreting the law? Thomas Jefferson didn't think so:

To consider the judges as the ultimate arbiters of all constitutional questions [is] a very dangerous doctrine indeed, and one which would place us under the despotism of an oligarchy. Our judges are as honest as other men and not more so. They have with others the same passions for party, for power, and the privilege of their corps… and their power the more dangerous as they are in office for life and not responsible, as the other functionaries are, to the elective control. The Constitution has erected no such single tribunal, knowing that to whatever hands confided, with the corruptions of time and party, its members would become despots. It has more wisely made all departments co-equal and co-sovereign within themselves

The branches may be co-equal, but that does not mean that any power possessed by any of them is equally possessed by them all. In interpreting the Constitution, the Supreme Court can only be supreme or inferior. Unless its decisions on the meaning of the Constitution are considered binding on the other branches, the Court has no power to interpret or defend the Constitution, other than when the other branches allow it. Congress can pass laws and initiate Constitutional amendments, and the executive branch has people with guns, but all the Supreme Court can do is issue opinions and expect them to be followed. The binding power of its decisions is the only power it has.

Also, if the Supreme Court can only be supreme or inferior in interpreting the Constitution, it should remain supreme. Leaving the final decision to the Supreme Court does not guarantee a correct outcome or a good outcome, but as long as the justices are chosen for their intelligence and for knowing and understanding the law (which is, at least, more true than it is in congressional and presidential elections), keep self-imposed traditions requiring consistency and thoughtfulness, and make a point of explaining the reasoning of their decisions (requiring some kind of logic, even if it is tortured, to actually exist), the Constitution is probably safer in their hands than it is in the hands of Congressmen and Presidents. I like Thomas Jefferson, but sometimes, he got carried away.