La. Stat. tit. 38 § 472
The improvement bonds shall be authorized by a resolution of the board of commissioners of the district, and the resolution shall be promulgated by one insertion in a newspaper of general circulation published in the district. For a period of sixty days from the date of publication of the resolution, any person in interest may contest the legality of the bonds or of the tax authorized for the payment thereof for any cause. After this time, no one shall have any cause or right of action to contest the regularity, formality, or legality of the bond authorization or the tax provision for any cause. If the validity of the tax or bond issue is not contested within the time delay set forth in the constitution, the authority to issue the bonds, the legality thereof, and of the taxes necessary to pay the bonds shall be conclusively presumed, and no court shall have authority to inquire into these matters.
La. R.S. § 38:472