It is unlawful and a misdemeanor for any person to obstruct, impede or interfere with any officer, employee, contractor or authorized representative of the city, or with any person who owns or holds any estate or interest in any building which has been ordered repaired, secured, vacated or demolished under the provisions of this chapter whenever such officer, employee, contractor or authorized representative of the city, person having an interest or estate in such building or structure, or purchaser is engaged in the work of repairing, vacating and repairing, or demolishing any such building, pursuant to the provisions of this chapter, or is performing any necessary act preliminary to or incidental to such work or authorized or directed pursuant to this chapter. (Prior code § 50.07.703)