This order was valid b/c national defense & defense of those joined w/us are jeopardized & imperiled. Under this view, the president is left powerless at the very moment that the need for action is most pressing. He is powerless b/c power not expressly given to Congress is found to reset exclusively w/it.
The whole of the “executive power” is vested in President & it was deliberately fashioned as an office of power & independence (“preserve, protect, defend” Art I, sec. I)
The Pres. executes laws of  Congress b/c the Constitution, not Congress, directs him to.