-FISA — 50 U.S.C. Ch. 36 (§ 1801 et seq.)
-FISA Section 702 — 50 U.S.C. § 1881a
-National Security Letters — 18 U.S.C. § 2709, 50 U.S.C. § 3162, 12 U.S.C. § 3414, 15 U.S.C. §§ 1681u–v
These are the federal statutes which allow this to be theoretically possible