46 U.S.C. § 53705
Pledge of United States Government
(a) Full Faith and Credit.—
The full faith and credit of the United States Government is pledged to the payment of a guarantee made under this chapter, for both principal and interest, including interest (as may be provided for in the guarantee) accruing between the date of default under a guaranteed obligation and the date of payment in full of the guarantee.
(b) Incontestability.—
A guarantee or commitment to guarantee made under this chapter is conclusive evidence of the eligibility of the obligation for the guarantee. The validity of a guarantee or commitment to guarantee made under this chapter is incontestable.
( Pub. L. 109–304, § 8(c) , Oct. 6, 2006 , 120 Stat. 1606 ; Pub. L. 109–163, div. C, title XXXV, § 3507(a)(1)(C) , Jan. 6, 2006 , 119 Stat. 3555 ; Pub. L. 110–181, div. C, title XXXV, § 3522(b) , Jan. 28, 2008 , 122 Stat. 598 .)