Bonds issued under the provisions of this act [21-7-13, 21-7-14, 21-7-16 to 21-7-25 NMSA 1978], being for the sole purposes specified in Section 1 [21-7-13 NMSA 1978] hereof, shall forever be and remain free and exempt from taxation by this state or any subdivision thereof.
NMS § 21-7-25