You misunderstand. I'm referring to your use of the word "treason", itself, as though it were emotionally defined rather than legally defined. Whether an act should have been considered treason in 1860 can only be determined by prior law as developed up to that point in time. A negotiated surrender in 1865 does not retroactively change the law. Your argument is perfectly consistent with my First Rule of Arguing With Yankees: All pro-union arguments eventually defy the rules of causation and will usually require sort of time travel.
“treason in 1860 can only be determined by prior law as developed up to that point in time.”
Article III Section 3 of the Constitution of the United States “Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.”
Is that prior enough for this discussion?
Ah. That explains how the war came to be about "slavery" nearly two years after Lincoln started it!
"Time Travel." Yup, that would do it.