26 CFR § 1.149(b)-1 - Federally guaranteed bonds.
(a) General rule. Under section 149(b) and this section, nothing in section 103(a) or in any other provision of law shall be construed to provide an exemption from Federal income tax for interest on any bond issued as part of an issue that is federally guaranteed.
(b) Exceptions. Pursuant to section 149(b)(3)(B), section 149(b)(1) and paragraph (a) of this section do not apply to -
(1) Investments in obligations issued pursuant to § 21B(d)(3) of the Federal Home Loan Bank Act, as amended by § 511 of the Financial Institutions Reform, Recovery, and Enforcement Act of 1989, or any successor provision; or
(2) Any investments that are held in a refunding escrow (as defined in § 1.148-1).
(c) Effective date. This section applies to investments made after June 30, 1993.