More from Texas v. White:(emphasis added)
“Did Texas, in consecuence of these acts, cease to be a State? Or, if not, did the State cease to be a member of the Union? It is needless to discuss, at length, the question whether the right of a State to withdraw from the Union for any cause, regarded by herself as sufficient, is consistent with the Constitution of the United States.
The Union of the States never was a purely artificial and arbitrary relation. It began among the Colonies, and grew out of common origin, mutual sympathies, kindred principles, similar interests, and geographical relations. It was confirmed and strengthened by the necessities of war, and received definite form, and character, and sanction from the Articles of Confederation. By these the Union was solemnly declared to ‘be perpetual.’ And when these Articles were found to be inadequate to the exigencies of the country, the Constitution was ordained ‘to form a more perfect Union.’ It is difficult to convey the idea of indissoluble unity more clearly than by these words. What can be indissoluble if a perpetual Union, made more perfect, is not?
But the perpetuity and indissolubility of the Union, by no means implies the loss of distinct and individual existence, or of the right of self-government by the States. Under the Articles of Confederation each State retained its sovereignty, freedom, and independence, and every power, jurisdiction, and right not expressly delegated to the United States. Under the Constitution, though the powers of the States were much restricted, still, all powers not delegated to the United States, nor prohibited to the States, are reserved to the States respectively, or to the people. And we have already had occasion to remark at this term, that the people of each State compose a State, having its own government, and endowed with all the functions essential to separate and independent existence,’ and that ‘without the States in union, there could be no such political body as the United States.’ Not only, therefore, can there be no loss of separate and independent autonomy to the States, through their union under the Constitution, but it may be not unreasonably said that the preservation of the States, and the maintenance of their governments, are as much within the design and care of the Constitution as the preservation of the Union and the maintenance of the National government. THE CONSTITUTION, IN ALL ITS PROVISIONS, LOOKS TO AN INDESTRUCTABLE UNION, COMPOSED OF INDESTRUCTABLE STATES.
When, therefore, Texas became one of the United States, she entered into an indissoluble relation. All the obligations of perpetual union, and all the guaranties of republican government in the Union, attached at once to the State. The act which consummated her admission into the Union was something more than a compact; it was the incorporation of a new member into the political body. And it was final. The union between Texas and the other States was as complete, as perpetual, and as indissoluble as the union between the original States.”
Thus, whether one agrees with the logic or not, it is clear the court has determined that absent complete consent by the other states or the U.S. being conquered by a foreign power, there is no legal way for a state or states to legally secede from the Union. So your “check in but can’t check out” comparison is correct.
Also, you misunderstand the court’s references to the “outbreak of the rebellion.” In 1868, while the war was over, the southern states were still largely under military occupation. I don’t have the date of Texas’ readmission to the Union handy, but I’ll bet it was after 1868. The formality of re-ratifying the constitution, with the amendments revoking slavery and recognizing the rights of former slaves, was yet to occur. The court’s attitude was merely a recognition of the hostilities that followed the attempt to secede, and the difficulties that ensued.
A more modern reason for opposing secession and the court determining it is illegal is the issue of the rights guaranteed by the 14th amendment (that is, “equal protection”). Because the 14 amendment was not ratified until after the war, and not litigated until the mid-20th century, the “Texas v. White” court could not have imagined this. But if an individual state wanted to remove itself from the federal government, there would no longer be a guarantee that the state would protect the consstitutional rights of the U.S. citizens living within its borders (purportedly, the entire population). Thus, any act of a state which would alter the legal status of its citizens vis a vis the federal government would be a per se violation of equal protection.
Then, there’s the issue of treason, which is specifically prohibited by the Constitution . . .
