To the extent allowed by federal law, a bank, insured savings institution, or credit union may act as a trustee or custodian of health savings accounts established with financial institutions under § 223 of the United States Internal Revenue Code of 1986, as amended from time to time, and medical savings accounts established with financial institutions under § 220 of the United States Internal Revenue Code of 1986, as amended from time to time. Contributions may be accepted and interest thereon retained by such institution pursuant to forms provided by it and may be invested in accounts of the institution in accordance with the terms upon which such contributions were accepted. The financial institution shall administer such accounts in accordance with the requirements of federal law.