> Practically and legally, everything Congress does is jammed through Article I Section 8 of the Constitution, which grants it the authority to "regulate" interstate commerce.
Actually, virtually all of Congress' enumerated powers are in Article I, Sec. 8. The interstate commerce clause, specifically, is unlikely to be cited in a defense of the NSA -- more likely, the Necessary Proper Clause of Art. I, Sec. 8, along the military powers in the same section (and the obligation to protect the states against invasion in Art IV, Sec. 4) would be more likely -- those who view the designation of the President as Commander-in-Chief of the military in Article II as a power of that office might be inclined to cite that "power" along with the Necessary and Proper Clause of Art. I, Sec. 8, instead.
Actually, virtually all of Congress' enumerated powers are in Article I, Sec. 8. The interstate commerce clause, specifically, is unlikely to be cited in a defense of the NSA -- more likely, the Necessary Proper Clause of Art. I, Sec. 8, along the military powers in the same section (and the obligation to protect the states against invasion in Art IV, Sec. 4) would be more likely -- those who view the designation of the President as Commander-in-Chief of the military in Article II as a power of that office might be inclined to cite that "power" along with the Necessary and Proper Clause of Art. I, Sec. 8, instead.