As I recall, the theory that the July 1861 Congress used was that the former States in secession had ceased to be "organized states." Although they remained the territory of the United States, they longer warranted representation in the Houses of Congress, and no longer counted toward total membership. This was consistant with how the territories were administered.Interesting. Those states were obviously never 'not states' and the claim that secession is invalid presents the paradox. All the lofty rhetoric about restoring the union when those who 'never left' had been relegated to the status of territories.
I think that Non-Seq would have a problem with this, as he continues to harp on the need of the secessionists to go before the courts and render judgement prior to leaving on the appropriate steps required for leaving. If all that is required for alteration of the status of a state is a simple majority of a very small fraction of congress, then where does that leave us?
I think the term used today, to describe that situation is "devolution." The context was in response to the question of "quorum" in the House and Senate. It is clear that from July 1861, until the states were "re-admitted" (re-qualified, re-organized, or whatever) the rebel states did not count toward total membership and quorum determination. Organized and unorganized territories have different levels of administration. These range from commissioners to appointed governors to self-elected governors. In some cases they can send non-voting members to the House of Representatives. After secession, the Federal government never recognized the validity of the rebel state governments or the CSA. hence, those opoulations fell back under the term "unorganized territory of the United States." That is how I recall the logic used - but I have not gone back to research the specifics.
In any case, as I cited in an earlier post, U.S. Grant in his memoirs wrote that if the South had debated secession honestly and asked out, they might have gotten it. Instead they took a unilateral course and sought to seize the assets (physical and military) of people of the United States. It was a gamble, and the South was doomed to lose in the long run.
Non sequitur presents one lawful way, among several, the South could have accomplished this.