(1) Notwith~tanding anything contained in any law for tiLe 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 rtlation to that building or after it h as been re·erected, su~lrt that building or alienate h1s nghts m respect of that buitdiJlg with~ ~ out the previous permission i11 writing of the competent a\lthonty.
(2) If the t~nant of any bu1lding sub-lets that buildmg or portion thereof or alienates his 1 ight m respect of that building or portion thersof in ~ contravention vf sub sectmn (I), such sub.lease or alienation shall be irivaUd l.J' and ~uch building or portion of building or, as tht case may be, suLh rights shall rev~ct to the owner of such building or vortion.