71 Pa. Stat. § 1707.14
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 for the construction, extension, improvement, equipping, furnishing or enlargement of any project or part thereof, that the Commonwealth will not limit or alter the rights hereby vested in the Authority until all bonds at any time issued, together with the interest thereon, are fully met and discharged. The Commonwealth 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 construction, extension, improvement, equipping, furnishing or enlargement of any project, or any portion thereof, the Commonwealth will not alter or limit the rights and powers of the 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 and any such Federal agency, and the 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.
71 P.S. § 1707.14