La. Stat. tit. 33 § 3835
No contest or proceeding to question the validity or legality of any resolutions or ordinances adopted or proceedings had under the provisions of R.S. 33:3822 through 33:3835 shall be begun in any court by any person for any cause whatsoever, after the expiration of thirty days from the date when the resolution, ordinance or proceeding was published, and after such time the regularity of such resolution, ordinance, or proceeding shall be conclusively presumed. If the validity of any certificates or amortized notes issued under the provisions of R.S. 33:3822 through 33:3835 is not raised within thirty days from the date of publication of the resolution or ordinance authorizing the issuing of said certificates or amortized note and fixing their terms, the authority to issue said certificates or amortized note, the legality thereof and of the local or special assessments necessary to pay the same shall be conclusively presumed and no court shall thereafter have authority to inquire into such matters.
La. R.S. § 33:3835