La. Stat. tit. 38 § 1867
For a period of sixty days from the date of the promulgation of the result of any election held under the provisions of this Part, any person in interest may contest the legality of the election, the assumption of debt provided hereunder or the tax authorized, for any cause. After this time, no one shall have any cause or right of action to contest the legality, formality, or regularity of the election, debt assumption, or tax levy, for any cause whatsoever. If the validity of any election, debt assumption, or tax levy authorized or provided for under the provisions of this Part is not raised within the sixty days herein prescribed, the authority to assume the debt, the regularity thereof and of the taxes necessary to pay the debt shall be conclusively presumed and no court shall have authority to inquire into the matters. If any resolution be adopted or proceeding had more than thirty days after the promulgation of the result of the election, no contest, action, or proceeding to question the authority of legality of the resolution or proceeding so adopted 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 was adopted or proceeding had.
La. R.S. § 38:1867