There would have to be a *HUGE* NBC attack, with casualties in the millions, in order for the courts to no longer be able to operate, thus de facto suspending the writ of habeus corpus and entering us into martial law.
Even if such an attack befell a region of the country, martial law would only apply to that region, and the courts, and the constitutional and democratic process would proceed elsewhere.
But a thread like this is good for identifying your rabid foam-at-the-mouth Bush haters (of which I am slightly to the right of
).