48 CFR 25.501: 25.501 General.

The contracting officer—

(a) Must apply the evaluation procedures of this subpart to each line item of an offer unless either the offer or the solicitation specifies evaluation on a group basis (see 25.503);

(b) May rely on the offeror's certification of end product origin when evaluating a foreign offer;

(c) Must identify and reject offers of end products that are prohibited in accordance with subpart 25.7; and

(d) When trade agreements are involved, must not use the Buy American statute evaluation factors prescribed in this subpart to provide a preference for one foreign offer over another foreign offer.