Minn. Stat. § 469.160

The validity of bonds or notes issued under sections 469.152 to 469.165 shall not depend on nor be affected by the validity or regularity of any proceedings relating to the acquisition, purchase, construction, reconstruction, improvement, betterment, or extension of the project for which they are issued. The ordinance or resolution authorizing the bonds or notes may provide that the bonds or notes shall contain a recital that they are issued pursuant to sections 469.152 to 469.165 , and the recital shall be conclusive evidence of their validity and of the regularity of their issuance.