> At the time it could have been easily argued that it was omitted from the constitution for a reason, one being that the southern states wouldn't have signed it.

That does not appear to be the case. Federalists were pretty clear that there would be no right to secession under the constitution. This is why anti-federalists in New York pushed to add language to New York's ratification that stipulated it's right to withdraw. James Madison argued that "the Constitution requires an adoption in toto, and for ever" and New York ended up ratifying the constitution without that language.

So your argument here hinges on the assertion that despite their clear statements to the contrary, the federalists left ambiguity about secession in the constitution to win over anti-federalists. I don't see any evidence to back this up.

Indeed, if the Southern states though they had the right to unilaterally secede under the constitution, they would have taken a case to the supreme court. They did not and when a case did make it to the supreme court afterwards, it was confirmed.

> In the US, actions are default legal unless explicitly deemed otherwise by law and there was no law or ruling, particularly an explicit one

That isn't how it works. There are general laws that cover a wide range of acts. When a court rules that a specific act falls under a law, the defendant doesn't get off because they committed the act before the ruling.

> Ask yourself this, why were no CSA politicians or military personnel ever brought up on charges of treason?

Because Andrew Johnson pardoned them to promote reconciliation and healing. Perhaps we would have been better of if they had been prosecuted for treason and we had traded short term animosity for justice and long term clarity.

> Again you are looking at history through modern eyes and trying to apply modern sensibilities to it.

How so? There was widespread condemnation of slavery at the time. What "modern" views am I imposing?

> Victim is such an overused word today. We were having a good discussion, why would you throw that angle in it?

That is precisly the angle that the effort to frame the civil war as a "war of nothern aggression" takes. You are repeating many of those talking points and factual mistakes so it seems highly relevant.

> There are still major countries where slavery exists today.

The "modern slavery" described in that article is substantially different from what was practiced in the South and there has been significant, if insufficient, international pressure put on those countries to change.

> Of course had they been allowed to secede, which wasn't confirmed to be illegal at the time, no one would have died.

What ifs are hard. There was far more to resolve about the secession than the possession of fort Sumter. Since the South had already demonstrated their willingness to use violence to get their way when they weren't satisfied with negotiations, it is hard to see how a path to peace could have existed.

If the southern states hadn't resorted to violence, would Lincoln have had the support to prosecute the war? If the southern states had tried to establish the legality of that secession they could have won and Lincoln would have had even less support.

The southern states seceded premptively without a legal basis because they lost an election and then chose to premptively start the violence and initiate a war.

The southern leaders who made those choices deserve full responsibility for that path.

The north had few choices. Secession movements were not limited to the South and establishing the precent of allowing them would have lead to the dissolution of the nation. This view of secession was shared by numerous presidents before Lincoln, including James Buchanan, who was a supporter of states rights regarding slavery.

> In order to justify secession as a constitutional remedy, it must be on the principle that the Federal Government is a mere voluntary association of States, to be dissolved at pleasure by any one of the contracting parties. If this be so, the Confederacy [here referring to the existing Union] is a rope of sand, to be penetrated and dissolved by the first adverse wave of public opinion in any of the States. In this manner our thirty-three States may resolve themselves into as many petty, jarring, and hostile republics, each one retiring from the Union without responsibility whenever any sudden excitement might impel them to such a course. By this process a Union might be entirely broken into fragments in a few weeks which cost our forefathers many years of toil, privation, and blood to establish.

So Lincoln was faced with either going to war to prevent secession or letting the US dissolve and this choice was readily clear to all involved.

Perhaps it would have been more moral to chose to save the 700k lives than to save the nation. I guess the answer to that question depends on how much of a patriot your are.

I personally think that intra state wars would have eventually broken out that would have cost more lives, but again, what ifs are hard.