Congress is also empowered to "raise and support Armies," and "provide and maintain a Navy."
International law can have a domestic effect when incorporated by the Supremacy Clause of the Constitution.
Various statutes are applicable in the national security law field including, but not limited to: There are a litany of Supreme Court and lower court cases which affect national security law.
The landmark case that deals with separation of powers between Congress and the President is Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952), also commonly referred to as The Steel Seizure Case, in which the United States Supreme Court limited the power of the President of the United States to seize private property in the absence of either specifically enumerated authority under Article Two of the United States Constitution or statutory authority conferred on him by Congress.
[1] Justice Jackson's concurring opinion is often quoted as it divided Presidential authority vis-à-vis Congress into three categories (in descending order of legitimacy):