That's why the FISA Act and the Patriot Act are careful to use the term of art "foreign intelligence information." THis is not the same thing as "intelligence" in general. At any rate, the "foreign" aspect of that is inserted to facilitate the statute tracking established case law and the historical understanding of the Constitution.
The President's power to unilaterally use force is strongest (least apt to be questioned) when directed to an extra-territorial enemy of the state. The War on Terror rasies some issues as to the limits of unchecked executive power that have heretofor not been carefully probed. IMO, it is unreasonable to expect the limits of conduct to be accurately described by statute, because the people have a more flexible notion of what it takes to "get 'r' done" than statutes can account for.
I actually think it is healthy to the Republic, in the long run, for some officials to overstep their bounds from time to time. That gives opportunities to exercize the corrective measures in the Constitution. If the system isn't exercised, it atrophies. See, e.g., the reluctance on the part of Congress to impeach judges.
If the people are okay with Kelo, Roe, and assorted other incursions, then that is the regulation they will get from their government.