[kato13]

Has Cummings ever called himself President? I just looked over Gateway to the Spanish Main and he is always called something like

"current Chairman of the Joint Chiefs of Staff and defacto Commander of the
Military Government of the United States"

Edit.

Also is Congress required? The text from part one states
" The President, however, is commander-in-chief of the military, and it has been argued that the President can take it upon himself to declare martial law. In these times, Congress may decide not to act, effectively accepting martial law by failing to stop it;"

That being said a Senate quorum should have been been able to have been assembled. Even if you place a high TDM casuality rate of 65% for senators and Governors (Really High IMO), you should still be able to get 51 senators given governors can appoint any replacements. (Estimated 35 Senators + 22 Replacements on average)

Again canon says nothing about this, but this is not a surprise war. I cannot imagine those types of death rates given the strikes stated and Nukes were flying for 5 months prior. IMO someone would have pre approved martial law or made arrangements for a quorum to be available for many strike scenarios.