42 C.F.R. § 435.340
Protected medically needy coverage for blind and disabled individuals eligible in December 1973
If an agency provides Medicaid to the medically needy, it must cover individuals who—
(a) Where eligible as medically needy under the Medicaid plan in December 1973 on the basis of the blindness or disability criteria of the AB, APTD, or AABD plan;
(b) For each consecutive month after December 1973, continue to meet—
(1) Those blindness or disability criteria; and
(2) The eligibility requirements for the medically needy under the December 1973 Medicaid plan; and
(c) Meet the current requirements for eligibility as medically needy under the Medicaid plan except for blindness or disability criteria.