Texas v. White was a lot more complex than that; Specifically, the court claimed that the Constitution, in its effort to "form a more perfect union," precluded secession. Secession was inherently unconstitutional, because its foundations are that the "more perfect" union is imperfect and not salvageable by any action - short of divorce.
Supreme Court Justice Salmon P. Chase in 1869, Chief Justice at the time:
"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. There was no place for reconsideration or revocation, except through revolution or through consent of the States."
I understand what the Supreme Court said. There are a few problems with it though.
1. The founders wholly rejected that notion. The Declaration of Independence says
>When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation
>That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness
>But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.
The Colonies were allowed to rid themselves of the British Government but the states aren't allowed to rid themselves of the American government? That makes no sense. The Founding Fathers would have had no issue with secession. Either the American Revolution was illegitimate or the southern one was legitimate. The British Empire made the same argument that the Supreme Court did. The British were wrong just like the Court.
2. If a state cannot leave, then how did the Southern States become military districts? Where in the Constitution does it give the federal government the right to strip states of statehood?
3. There was consent of the states who left to leave. I'm not sure why another state needs to be involved since the 10th amendment doesn't require the consent of other states.
4. If you have a glass of water. You take a sip of water you still have a glass of water. If a state leaves the Union you still have a union. If changing the amount of state destroys the union then I am not sure how adding to the Union does not do the same.
The Supreme Court ruled this way to provide cover for the unconstitutional actions of the federal government. They banned actions that were both allowed and they themselves did. To use a word from the Deceleration of Independence, that is despotism.
>2. If a state cannot leave, then how did the Southern States become military districts? Where in the Constitution does it give the federal government the right to strip states of statehood?
This was a key point that the 90s Republic of Texas movement keyed on, and they would tell anyone within earshot about why all Texas flags in courts are trimmed in gold fringe.
Supreme Court Justice Salmon P. Chase in 1869, Chief Justice at the time:
"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. There was no place for reconsideration or revocation, except through revolution or through consent of the States."