Re FISA, I can only quote:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Doesn't the Oath of Office, which pledges one to support the constitution, also cover the Amendments?