In the first palce I don't think that the the Full Faith & Credit Clause has the meaning you thought it had. Article IV, Section 1 says:
Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.
That requires each state to recognize the ations of another state. But since Virginia was in rebellion, and the leaders who had been elected were the ringleaders of that rebellion, then under the second sentence then Congress might actually have the power to determine if the proceedings leading to the creation of the reformed Virginia legislature were legal and base it's recognition on that.
Your broad interpetation of Ex Parte Milligan is as irrelevant as it is inaccurate. The Constitution wasn't suspended, far from it. The requirements in Article IV, Section 3 were followed. The question isn't if the actions of Congress were constitutional since they clearly were. The question is if the reformed Virginia legislature was legal and I haven't seen anything that indicates that they were not. If you can cite which laws were broken then I would like to hear them.
Other sources make it look like the work of an ad hoc convention. that would incline me, at least at first, to say "not OK."
So I've changed my mind to undecided.
Anyone out there have better sources on this key question?
It's nice to be learning something, and not just going back and forth, more or less unpleasantly!
Cheers,
Richard F.
If you can cite which laws were broken then I would like to hear them.
Are we back to this again? That there must be a law prohibiting something or else it's legal? In that case - please cite the Federal law prohibiting secession.