That is of course not what I said; "valid" a complicated question, depending on whether we want to get all land acknowledgement and question whether any of the US should have existed at all, including but not limited to the slave states.

An example of "valid" secession is the split of Czechoslovakia.

"Peaceful" is introducing a what-if about whether and why the Confederacy started the actual armed conflict part of the secession.

I have introduced a line break into the original comment as a demilitarized zone.

(we can also see the sort of "historical sliding window" effect as to legitimacy here. At what point does de facto line on the ground become baked in to legitimacy? Does California have a right to exist? Clearly more so than the occupation of Crimea, but is it just time that makes it so?)