For your review and/or enjoyment:
To steal Professor Orin Kerr's synopsis of the arguments:
[i]Here is the administration's argument in a nutshell:
First, the President has inherent constitutional authority to order foreign intelligence surveillance monitoring. The President's core job is to protect the country against foreign attack. The 9/11 attacks made this interest particularly strong: Al Qaeda is a clandestine enemy, and we need to gather intelligence to stop them. The Authorization to Use Military Force further emphasized this power: it brought foreign intelligence surveillance from Steel Seizures Category II to a Steel Seizures Category I, in which the President's authority is at a maximum. The AUMF confirms and bolsters the President's authority; under the test announced in Justice O'Connor's concurrence in Hamdi, foreign intelligence surveillance is a classic "fundamental incident of war" that the AUMF authorizes. The combination of the President's Commander-in-Chief power and Congress's explicit authoritization in the AUMF gives the President full authority to conduct this monitoring.
Further, the monitoring doesn't violate FISA and also complies with the Fourth Amendment. FISA itself is on fragile constitutional ground, and in any event the AUMF is a "statute" that authorizes the monitoring. Further, the so-called exclusivity provision of the wiretap act, 18 U.S.C. 2511(2)(f), doesn't trump this commonsense result. The legislative history of the section was focused on the notion of Congressional authorization, which the AUMF provided, and a contrary reading would create serious constitutional questions. The canon of constitutional avoidance requires construing the statutes to allow this sort of surveillance: the constitutionality of a statutory prohibition on such monitoring presents very difficult questions, as the NSA activities lie at the core of the Commander in Chief power. There are few guideposts here, and courts should construe the statute in a way to avoid having to reach these difficult constitutional questions. FISA is unconstitutional to the extent it directly interferes with the President's constitutional duty, and it would be prudent to construe the statute in a way that avoids these constitutional questions.
Finally, the monitoring program fits within the Fourth Amendment "special needs" exception. The rule here is reasonableness, which requires a balancing of governmental and privacy interests. The program is reasonable: the government's interest in thwarting a future attack is overwhelming, and the monitoring itself has been tailored and subject to considerable internal review.[/i]