73 Pa. Stat. § 383
The Commonwealth does hereby pledge to and agree with any person, firm or corporation, or Federal agency subscribing to or acquiring the bonds to be issued by the authority or the financing authority for the acquisition or financing of any project or part thereof, that the Commonwealth will not limit or alter the rights hereby vested in the authority or the financing authority until all bonds at any time issued, together with the interest thereon are fully met and discharged. The Commonwealth of Pennsylvania does further pledge to and agree with the United States and any other Federal agency that, in the event that any Federal agency shall construct or contribute any funds for the acquisition or financing of any project or any portion thereof, the Commonwealth will not alter or limit the rights and powers of the authority or the financing authority in any manner which would be inconsistent with the continued maintenance and operation of the project, or the improvement thereof, or which would be inconsistent with the due performance of any agreements between the authority or the financing authority and any such Federal agency, and the authority or the financing authority shall continue to have and may exercise all powers herein granted, so long as the same shall be necessary or desirable for the carrying out of the purposes of this act and the purposes of the United States in the acquisition or financing of the project or such portion thereof.
73 P.S. § 383