http://www.fas.org/irp/agency/doj/fisa/doj122205.pdf
This is a link to a .pdf of the letter that was sent to Senators Roberts and Rockefeller, and Congressmen Hockstra and Harmon of the Intelligence Committees on Dec 22. by William E Moschella, Assistant Attorney General
The letter, which cites many relevant statutes, stresses the word "reasonableness" -- as in "Intercepting communication into and out of the United States of persons linked to Al Queda in order to detect and prevent a catastrophic attack is clearly reasonable." [Page 4, paragraph 4]
I forgot to point out that the word "catastrophic" was in the same sentence.
Link to the same letter in HTML form with links to most of the cited cases ...