No person shall erect, alter or replace any structure within the city unless the structure complies with the applicable requirements of this code and the person has obtained a land use permit from the City Clerk certifying compliance with all of the applicable requirements of this code. No person shall use any structure or premises for any purpose other than as permitted by this code, except that lawful nonconforming uses as of the date of the adoption of this code may continue only as provided in M.S. § 462.357, Subd. 1e, as it may be amended from time to time.