48 CFR §9904.405-20

1. (a)The purpose of this Cost Accounting Standard is to facilitate the negotiation, audit, administration and settlement of contracts by establishing guidelines covering:
   1. (1)Identification of costs specifically described as unallowable, at the time such costs first become defined or authoritatively designated as unallowable, and
   2. (2)The cost accounting treatment to be accorded such identified unallowable costs in order to promote the consistent application of sound cost accounting principles covering all incurred costs.
2. (b)This Standard does not govern the allowability of costs. This is a function of the appropriate procurement or reviewing authority.