Ind. Code § 8-1.5-2-20

Sec. 20. Except as provided by section 22 of this chapter, the municipal legislative body may not adopt an ordinance, or enter into or ratify a contract, for the payment, directly or indirectly, of a bond or bonds by revenues derived by the municipality from the levy of taxes, from the issuance of any bonds other than from the issuance of bonds specifically authorized by this chapter or by a refunding statute, or from any source except the revenues derived from that particular utility.