From an article at:

https://www.law.cornell.edu/constitution-conan/article-2

"President Washington himself took command of state militia called into federal service to quell the Whiskey Rebellion, but there were not too many occasions subsequently in which federal troops or state militia called into federal service were required. Since World War II, however, the President, by virtue of his own powers and the authority vested in him by Congress, has used federal troops on a number of occasions, five of them involving resistance to desegregation decrees in the South.

In 1957, Governor Faubus employed the Arkansas National Guard to resist court-ordered desegregation in Little Rock, and President Eisenhower dispatched federal soldiers and brought the Guard under federal authority. In 1962, President Kennedy dispatched federal troops to Oxford, Mississippi, when federal marshals were unable to control with rioting that broke out upon the admission of an African American student to the University of Mississippi.

In June and September of 1964, President Johnson sent troops into Alabama to enforce court decrees opening schools to blacks. And, in 1965, the President used federal troops and federalized local Guardsmen to protect participants in a civil rights march. The President justified his action on the ground that there was a substantial likelihood of domestic violence because state authorities were refusing to protect the marchers."

(And let's not forget 1970 at Kent State, the muse for Neil Young's "Ohio" when Ohio was only under a State-level State of Emergency nor the killings at Jackson State just days later.)

Same article, paraphrased for brevity 'cause legalspeak…:

• martial law can be validly and constitutionally established by supreme political authority in wartime.-

The Supreme Court and the American judiciary embraced this theory that states declarations of martial law were conclusive and therefore not subject to judicial review.

In (the noted) case, the Court found that the Rhode Island legislature had been within its rights in resorting to the rights and usages of war in combating insurrection…"

POTUS has the legal right to do so nationally. There is also a strawman argument that civilian courts 'still' have primacy…not true. While there are certain areas of civilian operation that the military can't 'cooperate' in like undercover ops and such unless organized as such, the civilian courts, like all 'government services' stop functioning under Martial Law, habeus corpus is suspended and there is no need for a civilian court and thus cannot operate until the 'situation' is over. Until then, military justice reigns as do any sentences because a civilian court has no jurisdiction over a military court and thus cannot demand that a military tribunal conviction be overturned or handed to civilian courts for decision, after the fact.

The Comfort hospital ship wasn't filled with patients just so 'senior-killer-cuomo" could fulfill his part in the globalist 'destroy New York' play and kill off as many seniors as he could get away with…BUT the prison ship now just off GITMO will likely have fewer difficulties filling capacity volumes.