29 U.S.C. § 1133

In accordance with regulations of the Secretary, every employee benefit plan shall—

(1) provide adequate notice in writing to any participant or beneficiary whose claim for benefits under the plan has been denied, setting forth the specific reasons for such denial, written in a manner calculated to be understood by the participant, and

(2) afford a reasonable opportunity to any participant whose claim for benefits has been denied for a full and fair review by the appropriate named fiduciary of the decision denying the claim.

(Pub. L. 93–406, title I, §503, Sept. 2, 1974, 88 Stat. 893.)

Secretary authorized, effective Sept. 2, 1974, to promulgate regulations wherever provisions of this subchapter call for the promulgation of regulations, see section 1031 of this title.