I have seen on this thread the idea that the Supreme Court did not rule on State's rights until after the Civil War. May I put these items up for discussion?
The issue of State sovereignty and the integrity of the Union was answered by Chief Justice John Marshall in M'Culloch v. Maryland (1819):
"...In discussing this question, the counsel for the State of Maryland have deemed it of some importance, in the construction of the Constitution, to consider that instrument NOT AS EMANATING FROM THE PEOPLE BUT AS THE ACT OF SOVEREIGN AND INDEPENDENT STATES. The powers of the general government, it has been said, are delegated by the states, who alone are truly sovereign; and must be exercised in subordination to the states, who alone possess supreme dominion.
IT WOULD BE DIFFICULT TO SUSTAIN THIS PROPOSITION. ...The Convention, by Congress, and by the state legislatures the instrument was submitted to the PEOPLE. They acted upon it in the only manner in which they can act safely, effectively, and wisely, on such a subject-by assembling in convention. It is true, the assembled in their several states; and where else should they have assembled? No political dreamer was ever wild enough to think of breaking down the lines which separate the states, and of compounding the American people into one common mass. Of consequence, when they act, they act in their states. BUT the measures they adopt do not, on that account, cease to be the measures of the people themselves, or become the measures of the state governments. From these conventions the Constitution dreives its WHOLE AUTHORITY. THE GOVERNMENT PROCEEDS DIRECTLY FROM THE PEOPLE; IS ORDAINED AND ESTABLISHED IN THE NAME OF THE PEOPLE; AND IS DECLARED TO BE ORDAINED IN ORDER TO FORM A MORE PERFECT UNION, ESTABLISH JUSTICE, ENSURE DOMESTIC TRANQUILLITY, AND SECURE THE BLESSINGS OF LIBERTY TO THEMSELVES AND TO THEIR POSTERITY. The assent of the states, in their sovereign capacity, is implied in calling a convention, and thus submitting that instrument to the people. But the people were at perfect liberty to accept or reject it; and their act was final. It required not the affirmance, and could not be negatived, by the state governments. The Constitution, when thus adopted, was of complete obligation, and bound the STATE SOVEREIGNTIES. "...The powers delegated to the state sovereignties were to be exercised by themselves, not by a distinct and independent sovereignty created by themselves. To the formation of a league, such as was the Confederation, the state sovereignties were certainly competent. But when, IN ORDER TO FORM A MORE PERFECT UNION, it was deemed necessary to change this alliance into an effective government, possessing great and sovereign powers, and acting directly on the people, the necessity of referring it to the people, and of deriving its powers directly from them, WAS FELT AND ACKNOWLEDGED BY ALL."
THe CHief Justice further stated in Cohens v. Virginia (1821):
"...That the United States form, for many and for most important purposes, a single nation has not yet been denied. In war, we are one people. In making peace, we are one people. In all commercial regulations, we are one and the same people. In many other respects, the American people are one; and the government which is alone capable of controlling and managing their interests in all these respects is the government of the UNION. It is their government, and, in that character, they have no other. American has chosen to be, in many respects and to many purposes, a nation; and for all these purposes her government is complete; to all these objects it is SUPREME. It can, then, in effecting these objects, legitmately control all individuals or governments within the American territory. The constitution and laws of a state, so far as they are repugnant to the Constitution and laws of the United States, are ABSOLUTELY VOID."
Looks like the Supreme Court had already decided who was the law of the land, the people of the United States as represented by their government, not the individual States, way before the end of the Civil War.