42 C.F.R. § 403.768
Excluded services
In addition to items and services excluded in § 409.49 of this chapter, items and services are also excluded if they are provided by:
(a) A HHA that is not a RNHCI.
(b) A supplier who is not providing RNHCI designated items under arrangement with a RNHCI.
(c) A nurse who is not providing RNHCI home nursing services under arrangement with a RNHCI.