Martial law is easier said than done. Obstacles to such a course of action are more than you might think, including the blow back on Trump and the Republican Party if it, as is likely, broadly repudiated from many quarters of our society, not least from within state/governmental structures. It would constitute a shift from hegemonic rule, which includes an element of domination, to rule by domination exclusively, which is, if not said by its practitioners, an admission of weakness.