7 U.S.C. § 1928: Full faith and credit

(a) In generalA contract of insurance or guarantee executed by the Secretary under this chapter shall be an obligation supported by the full faith and credit of the United States. (b) ContestabilityA contract of insurance or guarantee executed by the Secretary under this chapter shall be incontestable except for fraud or misrepresentation that the lender or any holder—(1) has actual knowledge of at the time the contract or guarantee is executed; or (2) participates in or condones.