The United States Constitution implicitly provides some emergency powers in the article about the executive power :
Congress may authorize the government to call forth the militia to execute the laws, suppress an insurrection or repel an invasion.
Congress may authorize the government to suspend consideration of writs of habeas corpus “when in cases of rebellion or invasion the public safety may require it.”
Felony charges may be brought without presentment or grand jury indictment in cases arising “in the militia, when in actual service in time of war or public danger.”
A state government may engage in war without Congress’s approval if “actually invaded, or in such imminent Danger as will not admit of delay.”
Aside from these, many provisions of law exist in various jurisdictions, which take effect only upon an executive declaration of emergency; some 500 federal laws take effect upon a presidential declaration of emergency. The National Emergencies Act regulates this process at the federal level. It requires the President to specifically identify the provisions activated and to renew the declaration annually so as to prevent an arbitrarily broad or open-ended emergency. Presidents have occasionally taken action justified as necessary or prudent because of a state of emergency, only to have the action struck down in court as unconstitutional.[110]
From wiki
Earlier he made similar assertions concerning the President of the United States (a slight nuance indicating he was referring to powers of the OFFICE, not himself personally).
I am not a Constitutional Scholar, but I SUSPECT THAT THE LEGALITY OF THESE STATEMENTS IS DEPENDENT UPON THE FACT THAT WE ARE AT WAR.
Not metaphorical war.
Not "Moral equivalent of war."
Not a crisis of the proportions of war.
OUR PLAN OF COUNTERATTACK: We will defeat the communists by UNPLUGGING THEM from the world's capitalist economies so they can collapse like the USSR.