That reply in different words each time is what makes you so easy ha.
In 1869 the Supreme Court ruled that
unilateral secession is unconstitutional and, accordingly, illegal.
It was the case on appeal of Texas v White. Mr. White challenged the laws Texas had enacted during the Civil War. He said the laws were invalid because TX had seceded from the Union of the States. And that Mr. White, as a citizen of the United States FIRST AND FOREMOST and secondarily a TX citizen also, had been subjected to illegal and false laws imposed by a local government that was in an armed rebellion against the United States and therefore in violation of the Constitution.
The Court agreed with Mr. White. That is, the laws were illegal and false. And that was because Texas had seceded from the Union of the States in an act that the Court had to recognize as unconstitutional. Illegal. However, the Court said that UNILATERAL secession is unconstitutional. A state simply up and seceding on its own is unconstitutional. But that a state seceding under the James Madison formula would be constitutional.
Given Madison wrote the Constitution the Court turned to his letter of 1833 shortly before he died in that year, age 86. A state wishing to withdraw from the Union of the States would need to successfully petition two-thirds of each house of the Congress and three-quarters of the states in order to secede Constitutionally. Otherwise, no, secession would not be valid, accepted, allowed.
The Court accepted Madison's proposition that in a free state secession must be an option, that secession must be on the table. But that secession would be possible only by a mutual agreement among the states, which is the same principle and practice that the states accepted in adopting the Constitution and in ratifying it. Each state entered the Union by mutual agreement, and therefore a state can exit only by mutual agreement. All states being equal, each action affecting the membership of the whole needs to be mutual.
So your Kitchen Sink 10th Amendment catch-all for Rightwingers to exploit when all else fails remains as the litter box of the USA Constitution. Your failure to mention Texas v White also shows your ignorance in the matter of secession. And about the Tenth Amendment.