Indiana Code Title 36. Local Government § 36-10-8-15

Sec. 15. The Indiana general assembly covenants with the purchasers of any bonds issued under this chapter that the statute authorizing the levy of a specific tax within the county the proceeds of which are required by this chapter to be deposited in a specific fund created under this chapter will not be repealed, amended, or altered in any manner that would reduce or adversely affect the levy and collection of the tax levied, or reduce the rates or amounts of the tax, as long as the principal of, or interest on, any bonds is unpaid.  The board, on behalf of the county, is authorized to make a similar pledge or covenant in any agreement with the purchasers of any bonds issued under this chapter or in any resolution or trust agreement pursuant to which the bonds are issued.