> The negotiated rates must be accepted by all Federal awarding agencies. An HHS awarding agency may use a rate different from the negotiated rate for a class of Federal awards or a single Federal award only when required by Federal statute or regulation, or when approved by a Federal awarding agency head or delegate based on documented justification as described in paragraph (c)(3) of this section.
Subsection (c)(3), in turn, says:
> (3) The HHS awarding agency must implement, and make publicly available, the policies, procedures and general decision making criteria that their programs will follow to seek and justify deviations from negotiated rates.
Just based on a quick perusal it seems like the administration has a decent argument that the agency head can approve the 15% indirect by fiat as long as he or she comes up with a documented justification.