Earlier quoted context omitted.
So Marshall law means the US isn’t a democracy (which is true, being a republic)…
Democracy (as in will of the people) doesn’t really exist during wars on domestic soil. Martial Law declarations are at least the honest admission of that. And the democracy / republic pedantry is tiresome. We are a Democratic Republic (and also a Constitutional Republic). They are not mutually exclusive.
We’re a functionally plutocratic federal republic with some very loosely representative-democratic elements. Ironically, as a result of federal rules imposed on the states but not on the federal government itself, like one-person, one-vote, the states, while still more than a little plutocratic in practice, do a better job of approximating representative democracy in their formal structures (and many also have elements of direct democracy.)