La. Stat. tit. 33 § 3836
Any parish or municipal corporation, east of the Mississippi River, including any agency, instrumentality or board thereof, may enter into contracts for the purchase of water over periods of years not exceeding sixty. Payments under any such contract shall be measured by the amount of water annually made available to the parish or municipality and used or distributed by it, provided that a parish or municipality may agree, in such contract or any amendment thereto, to accept and pay for, in each future year during a period not exceeding the life of the contract, a minimum quantity of water per year. Such a contract may, but need not, provide for the granting to the parish or municipality of all or part of the facilities of the seller, with or without further consideration, but if payments are measured as above provided, such contract shall not be deemed the incurring of indebtedness or the borrowing of money and no approval of the State Bond and Tax Board or any other board or commission shall be required in order that such contract be effective. Such contract may, but need not, limit the sources from which payment for such water shall be made.
Any such contract may be authorized or ratified by resolution of the governing authority of the parish or municipality and such resolution (which shall refer to a contract or form of contract available for public inspection in the office of the parish or municipality) shall be published one time in a newspaper of general circulation in the parish or municipality. For a period ending thirty days after the publication of such resolution any person in interest shall have the right to contest the legality of such contract for any cause; after such time no one shall have any cause or right of action to contest the regularity, formality or legality of said contract for any cause whatsoever. If the validity of any such contract is not raised within the thirty days herein prescribed the authority to enter into such contract, the legality thereof and all covenants and obligations contained therein shall be conclusively presumed and no court shall have authority to inquire into such matters.
La. R.S. § 33:3836