Va. Code § 21-281
The Commonwealth does pledge to and agree with the holders of any bonds or other obligations issued by any commission pursuant to this chapter that the Commonwealth will not limit or alter the rights hereby vested in such commission to charge and collect such fees, rents and charges and other revenues as may be convenient or necessary in order to comply with the terms and provisions of any contract or contracts made by such commission with such holders, or in any way impair the rights and remedies of such holders, until the bonds and other obligations, together with interest thereon, with interest on any unpaid installments of interest, and all costs and expenses in connection with any action or proceeding by or on behalf of such holders are fully met and discharged.
Va. Code § 21-281