Restrictions
Nothing in this chapter shall be construed to constitute authorization hereunder for—
the use of the cost-plus-a-percentage-of-cost system of contracting;
any contract in violation of existing law relating to limitation of profits;
the negotiation of purchases of or contracts for property or services required by law to be procured by formal advertising and competitive bidding;
the waiver of any bid, payment, performance, or other bond required by law;
the amendment of a contract negotiated under section 2304(a)(15) 1
the formalization of an informal commitment, unless it is found that at the time the commitment was made it was impracticable to use normal procurement procedures.