Article II, Section 1, states that the executive powers shall be vested in the office of the president.

BUT nowhere does it say what those powers are and certain does not say that he has the power to issue executive orders which have the authority of law. Nor does it say that he has the power to call for 75,000 volunteers for the purpose of war without the authority of a Declaration of War which can only come from Congress.

the power to issue Executive orders are something that has been assumed appearently.