The states didn't rebel, they seceded from the Union as they had a perfect right to do. The Union didn't want them to so they pushed the South until a war started. The Union could have left the seceded states alone BEFORE a war started but they chose(or Lincoln did)to make sure a war started in order to force the states back into a Union they no longer wanted to belong to. If you join something you have the right to unjoin, but the Union didn't see it that way therefore there was a war, of the Union's making.
People didn't agree about whether such a "perfect right" existed. You can say it does and Jeff Davis could say it does, but that wasn't universally accepted. That's why there was a war.
The Union didn't want them to so they pushed the South until a war started.
Didn't take much pushing. It's highly possible that those Confederates leaders and firebrands wanted war. Look at some of the speeches. War would push or pull wavering states like Virginia or Tennessee into the Confederate camp.
I can't say for certain, but that must have at least crossed Davis's mind. Some of the Southern fire-eaters were passionate about war, which they thought would be short and glorious and victorious for them.
The Union could have left the seceded states alone BEFORE a war started but they chose(or Lincoln did) to make sure a war started in order to force the states back into a Union they no longer wanted to belong to.
Hey, when the fort doesn't surrender, just don't friggin' shoot at it. No war then.
If you join something you have the right to unjoin, but the Union didn't see it that way therefore there was a war, of the Union's making.
If you join the military you can't just up and leave. If you set up a partnership, you can't just decide on your own to take back what you think you put in and go your own way. If the bank tells you there's a significant penalty to early withdrawal when you buy a certificate of deposit, you can't take a gun into the branch office and demand all your money bank.
I certainly suppose a state could get out of the Union and sever its tie to the rest of the country. The question is whether it could do this unilaterally, on its own without the consent of the rest of the country, without negotiations about settling the questions that arise. There's no right to do that, and there certainly isn't -- and wasn't -- universal agreement that such a right exists or existed.