“Think of the recent Brexit vote.”
Poor analogy.
The EU treaty’s paragraph 50, lays out the procedures for formal and legal withdrawal from the European Union by a member state.. Great Britain is following the required procedures.
Did South Carolina follow the procedures laid out in the Consitution for withdrawing from the United States?
The Constitution is still silent on state secession.
The power to determine whether or not a state wishing you secede may do so is not specifically granted to the Federal Government. The Tenth Amendment states that any power not specifically granted to the Federal Government is reserved for the states or the people. Therefore, the power to determine whether a state may secede belongs to the state government.
Therefore there is a legal argument for secession. Where people have a problem is that we tend to judge historical events through the lens of our own perspective. The US simply wasn’t seen as a true nation by the people living here prior to the war. If you asked a farmer in the Shenandoah Valley where he was from, it would never have even crossed his mind to say “America”. His natural response would have been “Virginia”. That’s where the analogy to the EU comes in. I would guess that nobody in Europe calls themselves Europeans. It just isn’t a country. Admittedly the modern EU is more loosely united than the antebellum US was, but the political and legal analogy remains. It’s kind of an ex post facto justification to condemn the Confederacy for being traitorous since the legality of secession was an open question at the time it happened.
The US Constitution listed no such procedure because the topic was quite amply covered in the Declaration of Independence 11 years previously.
No further thing needed to be said about it in the US Constitution.