N.D. Cent. Code § 40-22-43

Defects and irregularities in any proceedings had or to be had under this chapter relating to municipal improvements by the special assessment method, when the proceedings are for a lawful purpose and are unaffected by fraud and do not violate any constitutional limitation or restriction, shall not invalidate such proceedings, and no action shall be commenced or maintained and no defense or counterclaim in any action shall be recognized in the courts of this state founded on any such defects or irregularities in such proceedings, unless commenced within thirty days of the adoption of the resolution of the governing board awarding the sale of warrants to finance the improvement.