La. R.S. 48:1157

The provisions of this Part and of any contract entered into under the authority hereof, shall constitute a contract between the state, the department, the authority which is a party to such contract, and the holders of any bonds, notes or other obligations of such authority. The holder or holders of any such bonds, notes or other obligations, may enforce the performance of such contract by appropriate action or civil proceeding. The validity of such contract or of any provision thereof shall not be questioned by any person in any action or civil proceeding after the expiration of sixty days from the date of its execution.