Which laws were they in violation of?
See my previous exposition on the Whiskey Rebellion, as I think that's a more clear (and in the terms of the mid-19th century, correct) definition of Rebellion or Insurrection. The politicians of 1863 certainly changed the meanings of both of these concepts, of course, so for us to look at it in terms of modern terminology is to rob it of quite a bit of it's accuracy.
Because they had not the power to unilaterally secede, regardless of their convention.
That was a topic that was hotly under debate back in the day. I refer you to the New York resolution ratifying the Constitution of 1787:
That the powers of government may be reassumed by the people whensoever it shall become necessary to their happiness; that every power, jurisdiction, and right, which is not by the said Constitution clearly delegated to the Congress of the United States, or the departments of the government thereof, remains to the people of the several states, or to their respective state governments, to whom they may have granted the same; and that those clauses in the said Constitution, which declare that Congress shall not have or exercise certain powers, do not imply that Congress is entitled to any powers not given by the said Constitution; but such clauses are to be construed either as exceptions to certain specified powers, or as inserted merely for greater caution.
As you can see, New York authorized itself the option of seceding from the Federal Constitution, should it feel the necessity of doing so.
I don't understand how you can claim that the federal government did not have jurisdiction over the people in the states.
Because the Federal government did not have absolute jurisdiction over every citizen in the nation, at the time. Citizens owed their allegiance first to their State, and second to the Federal government. (Obviously, this is not universal, as many examples of Southerners supporting the Union, and Northerners supporting the Confederacy have been found, but what I have described was the majority at the time.)
One of the Federalist papers touches on the relationship between the Federal government and the citizens of a State, and the State governments and its citizens. I can't recall which one it is offhand, but if I can find it later, I'll link to it and cite it. (In class right now. :) )
The New York resolution was full of declarations. No standing army. No suits against states. But in the end they ratified the Constitution as passed by the convention. And I would also point out that the ratification documents are not the law of the land, the Constitution is. If the ratification document reserves a power not granted to the states by the Constitution then the Constitution prevails.
Because the Federal government did not have absolute jurisdiction over every citizen in the nation, at the time. Citizens owed their allegiance first to their State, and second to the Federal government. (Obviously, this is not universal, as many examples of Southerners supporting the Union, and Northerners supporting the Confederacy have been found, but what I have described was the majority at the time.)
Obviously people like George Washington disagreed with you. And regardless of where people thought their loyalty laid, the fact of the matter is that the supremecy clause of the Constitution made it clear that the U.S. Constitution, and the laws made under it, trumped all local laws and state Constitutions where those laws and constitutions conflicted with it.