12 C.F.R. § 724.1
A federal credit union is authorized to act as trustee or custodian, and may receive reasonable compensation for so acting, under any written trust instrument or custodial agreement created or organized in the United States and forming part of a tax-advantaged savings plan which qualifies or qualified for specific tax treatment under sections 223, 401(d), 408, 408A and 530 of the Internal Revenue Code (26 U.S.C. 223 , 401(d) , 408 , 408A and 530 ), for its members or groups of its members, provided the funds of such plans are invested in share accounts or share certificate accounts of the Federal credit union. Federal credit unions located in a territory, including the trust territories, or a possession of the United States, or the Commonwealth of Puerto Rico, are also authorized to act as trustee or custodian for such plans, if authorized under sections 223, 401(d), 408, 408A and 530 of the Internal Revenue Code as applied to the territory or possession under similar provisions of territorial law. All funds held in a trustee or custodial capacity must be maintained in accordance with applicable laws and rules and regulations as may be promulgated by the Secretary of Labor, the Secretary of the Treasury, or any other authority exercising jurisdiction over such trust or custodial accounts. The federal credit union shall maintain individual records for each participant which show in detail all transactions relating to the funds of each participant or beneficiary.
12 C.F.R. §724.1