10 USC 2310 - Determinations and decisions

(a) Individual or Class Determinations and Decisions Authorized.— 
Determinations and decisions required to be made under this chapter by the head of an agency may be made for an individual purchase or contract or, except to the extent expressly prohibited by another provision of law, for a class of purchases or contracts. Such determinations and decisions are final.
(b) Written Findings Required.— 

(1) Each determination or decision under section 2306 (g)(1), 2307 (d), or 2313 (c)(2)(B) of this title shall be based on a written finding by the person making the determination or decision. The finding shall set out facts and circumstances that support the determination or decision.
(2) Each finding referred to in paragraph (1) is final. The head of the agency making such finding shall maintain a copy of the finding for not less than 6 years after the date of the determination or decision.