One argument that seems OK to me:
John Schmidt (Chicago Tribune):
In the Supreme Court?s 1972 Keith decision holding that the president does not have inherent authority to order wiretapping without warrants to combat domestic threats, the court said explicitly that it was not questioning the president?s authority to take such action in response to threats from abroad.
Four federal courts of appeal subsequently faced the issue squarely and held that the president has inherent authority to authorize wiretapping for foreign intelligence purposes without judicial warrant.
In the most recent judicial statement on the issue, the Foreign Intelligence Surveillance Court of Review, composed of three federal appellate court judges, said in 2002 that ?All the ... courts to have decided the issue held that the president did have inherent authority to conduct warrantless searches to obtain foreign intelligence ... We take for granted that the president does have that authority.?
The passage of the Foreign Intelligence Surveillance Act in 1978 did not alter the constitutional situation. That law created the Foreign Intelligence Surveillance Court that can authorize surveillance directed at an ?agent of a foreign power,? which includes a foreign terrorist group. Thus, Congress put its weight behind the constitutionality of such surveillance in compliance with the law?s procedures.
But as the 2002 Court of Review noted, if the president has inherent authority to conduct warrantless searches, ?FISA could not encroach on the president?s constitutional power.?