48 U.S.C. § 745: Tax exempt bonds

All bonds issued by the Government of Puerto Rico, or by its authority, shall be exempt from taxation by the Government of the United States, or by the Government of Puerto Rico or of any political or municipal subdivision thereof, or by any State, Territory, or possession, or by any county, municipality, or other municipal subdivision of any State, Territory, or possession of the United States, or by the District of Columbia.