Every act or thing done, or anything existing within the limits of any city referred to in ORS § 221.906, which is or may be declared by any law of this state or by any ordinance of such city to be a nuisance, hereby is declared to be a nuisance, and shall be considered and treated as such in all actions, suits and proceedings whatsoever, unless such law or ordinance is declared void by a court of competent jurisdiction.