The secessions were unlawful. After all, when the Northern states were compelled to return fugitive slaves to the South, that was done on the basis of text in the Constitution that was binding on all of the states (namely, about returning those fleeing from bondage to their masters).
In fact the Constitution included many regulations and prohibitions regarding the power of individual states, so it can't be claimed that the Constitution wasn't the ultimate arbiter of power within the federal framework of government.
So with that in mind a unilateral decision by a single state to change the Constitutional government for all of the states can hardly have been legal. And even the parts of the Constitution talking about the territorial integrity of a single state all include the clause the Congress must approve the change in addition to the state itself.
If a state really wanted to secede it would have to have come up with some legal procedure at the national level from which to even make that change possible. Probably by using the Constitutional Amendment process (which is, after all, the built-in designed mechanism for altering the federal framework of government).
A prisoner does not ask his warden for release. It would take enough hearts and minds to secede, and nothing else.
How it actually happens and whether or not different commenters find it "legal" will not matter. If I deny your jurisdiction and have the military force to defend myself, your laws do not apply to me.
> If I deny your jurisdiction and have the military force to defend myself, your laws do not apply to me.
Sure, this is how some sovereign states formed in the first place. But even these were made "legal" under international jurisprudence.
Don't confuse exercise of power with legal aspects though. It can certainly be against a nation's laws to secede, and secede anyways if you can prevent the state from effectively exercising power (e.g. Algeria in the 1950s). But that didn't make it "legal", either under domestic or international law.
Even in international law if you want to secede you have to form a separate state, have it exercise effective control over a territory, and do so long enough to have "enough" other nations recognize that control. If you can do that then it doesn't matter what your parent nation's domestic laws were, but until you can do that it's shaky legal ground indeed.
Citations please. Slavery is only mentioned twice in the Constitution, and then, it's Amendments 13 and 14 (passed after the end of the Civil War). Restrictions of power towards the several states is spelled out in Article I, section 10 (three paragraphs) and Article IV, with a clarification in Amendment X ("The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people.").
There is nothing in the Constitution about secession (including the Amendments).
I'm surprised you managed to make it to Article IV without finding the citation which you seek. I'll quote Art. IV, §2:
"No Person held to Service or Labour in one State, under the Laws thereof, escaping into another, shall, in Consequence of any Law or Regulation therein, be discharged from such Service or Labour, but shall be delivered up on Claim of the Party to whom such Service or Labour may be due."
This clause was made null and void by the Thirteenth Amendment that you've mentioned, which further makes me wonder...
Anyways, the word "slavery" was deliberately not used by the Framers, as even at that time the concept was morally distasteful, so the Framers talked around the issue by referring to "Service" and "Party" instead of "slave" and "master".
You also missed the part in the Constitution where importation of slaves could not be forbidden until 1808 (Art. I, §9).
In fact the Constitution included many regulations and prohibitions regarding the power of individual states, so it can't be claimed that the Constitution wasn't the ultimate arbiter of power within the federal framework of government.
So with that in mind a unilateral decision by a single state to change the Constitutional government for all of the states can hardly have been legal. And even the parts of the Constitution talking about the territorial integrity of a single state all include the clause the Congress must approve the change in addition to the state itself.
If a state really wanted to secede it would have to have come up with some legal procedure at the national level from which to even make that change possible. Probably by using the Constitutional Amendment process (which is, after all, the built-in designed mechanism for altering the federal framework of government).