29 C.F.R. § 1470.6 – Additions and exceptions.

(a) For classes of grants and grantees subject to this part, Federal agencies may not impose additional administrative requirements except in codified regulations published in the Federal Register.
(b) Exceptions for classes of grants or grantees may be authorized only by OMB.
(c) Exceptions on a case-by-case basis and for subgrantees may be authorized by the affected Federal agencies.