Tenants not to sub-let or alienate

(1) Notwithstanding anything contained in any law for the time being in force, or in any contract, no tenant of any building in a slum area shall, after the execution of any work of improvement in relation to that building or after it has been re-erected, sub-let that building or alienate his rights in respect of that building without the previous permission in writing of the competent authority. (2) If the tenant of any building sub-lets that building or portion thereof or alienates his right in respect of that building or portion thereof in contravention of sub-section (1), such sub-lease or alienation shall be invalid and such building or portion of building or, as the case may be such rights shall revert to the owner of such building or portion.