The State of California does hereby pledge to and agree with the holders of any bonds issued pursuant to this chapter that the state will not change the structure, organization, or powers of any district until all obligations on those bonds are fully met or discharged. However, this section does not preclude a change in the structure, organization, or powers of any district if adequate provision is made by law for the protection of the contracts represented by those bonds from impairment, and that right to change the structure, organization, or powers of any district or the allocation of those tax revenues is hereby reserved to the State of California. Districts may include this pledge of the state in those bonds.