I'm assuming that permissions is needed, based on my reading of the Constitution. And you're assuming permission isn't needed, based on your reading of the Constitution. The men at the Constitution themselves don't seem to have weighed in on the subject much, except James Madison who wrote several times against the idea of states being able to just walk out.
If the original constitution of Kansas wasn't really along the lines of a proper republic, they may have gotten refused for a time.
Actually the problem was free state/slave state. The first couple allowed slavery.
That does not negate the fact that ALL the states that entered the Union did so of their own free will and not by force, and thus could leave by their own free will.
One could just as easily make the case, and I have, that states were allowed to join the Union with the consent of the other states and thus could only leave with the consent of the other states. Free will is fine. But all the free will in the territory will not get them added as a state unless the other states OK it.
If you were to join a club, and even if they had to review your credentials and approve you before you became a member, that would not take away your right to leave the club later if you chose.
Unless the rules said leaving required consultations and approval of the other members.
From the fact that all power that the government has was delegated to the government by its creators, the states. Certain properties were delegated by the states to the fed gov for the fulfillment of its delegated duties (such as tax collection houses and military forts for the protection of the states). However, when the states reassumed their delegated powers, the federal government now had no right to maintain tax houses and forts and such in those states, as the power and right to do so had been withdrawn.
Article I, Section 8 makes it clear that Congress exercises sole authority over the property of the other states. There is nothing in there that says when states leave they can take what they want.
Except they weren't. They were also bringing more troops and ammunition.
Which Lincoln also mentioned in his letter and also made it clear that they would remain on the ship unless the resupply was opposed. Nothing was hidden from Pickens.
Unless the rules said leaving required consultations and approval of the other members.
But the Constitution says no such thing. It never touches the topic, because that topic falls under the Tenth Amendment, as a right left to the States. :-)
Article I, Section 8 makes it clear that Congress exercises sole authority over the property of the other states. There is nothing in there that says when states leave they can take what they want.
Remember, the constitution only applies to states while they are in the Union. Congress and the constitution has no power over anything in any state which has withdrawn its delegated powers.
Regarding Fort Sumter, here are a couple interested articles for you to read:
http://tenthamendmentcenter.com/2009/05/04/lincolns-war/
http://www.tulane.edu/~sumter/Reflections/LinWar.html
Lincoln in a letter to Gustavus Fox in May 1861. Fox was the commander of the expedition Abe sent to reinforce Ft. Sumter:
"You (FOX) and I both anticipated that the cause of the country would be advanced by making the attempt to provision Fort Sumter, even if it should fail ; and it is no small consolation now to feel that our anticipation is justified by the result (WAR) .