Ever since the New York Times published classified information in December 2005' about the efforts by the National Security Agency to intercept enemy communications to or from sources in the United States (as authorized by the President in his capacity as Commander-In-Chief), there has been a great hew and cry about the President's "illegal" conduct.
Eastman, John C.
"Listening To The Enemy: The President's Power To Conduct Surveillance Of Enemy Communications During Time Of War,"
ILSA Journal of International & Comparative Law: Vol. 13
, Article 3.
Available at: https://nsuworks.nova.edu/ilsajournal/vol13/iss1/3