45 CFR § 800.503 - External review.
(a) External review by OPM. OPM will conduct external review of adverse benefit determinations using a process similar to OPM review of disputed claims under 5 CFR 890.105(e), subject to the standards and timeframes set forth in 45 CFR 147.136(d).
(c) Issuer obligation. An MSP issuer must pay a claim or provide a health-related service or supply pursuant to OPM's final decision or the final decision of an independent review organization without delay, regardless of whether the plan or issuer intends to seek judicial review of the external review decision and unless or until there is a judicial decision otherwise.
The following state regulations pages link to this page.