45 C.F.R. § 800.109 – Network adequacy.

(a) General requirement. An MSP issuer must ensure that the provider network of each of its MSP options, as available to all enrollees, meets the following standards:
1. (1) Maintains a network that is sufficient in number and types of providers to assure that all services will be accessible without unreasonable delay;
2. (2) Is consistent with the network adequacy provisions of section 2702(c) of the Public Health Service Act; and
3. (3) Includes essential community providers in compliance with 45 CFR 156.235.
(b) Provider directory. An MSP issuer must make its provider directory for an MSP option available to the Exchange for publication online pursuant to guidance from the Exchange and to potential enrollees in hard copy, upon request. In the provider directory, an MSP issuer must identify providers that are not accepting new patients.
(c) OPM guidance. OPM will issue guidance containing the criteria and standards that it will use to determine the adequacy of a provider network.