Section 302. Unlawful occupation

1.  a. If any dwelling or structure be
  occupied in whole or in  part  for  human  habitation  in  violation  of
  section  three  hundred one, during such unlawful occupation any bond or
  note secured by a mortgage upon said dwelling or structure, or  the  lot
  upon  which  it  stands,  may  be  declared  due  at  the  option of the
  mortgagee.
    b. No rent shall be recovered by the owner of such premises  for  said
  period,  and  no  action  or  special  proceeding  shall  be  maintained
  therefor, or for possession of said  premises  for  nonpayment  of  such
  rent.
    c.  During  such period the department in charge of water supply shall
  not permit water to be furnished in any such dwelling or  structure  and
  said  premises  shall  be  deemed  unfit  for  human habitation, and the
  department of health or the department charged with the  enforcement  of
  this chapter shall cause them to be vacated.
    2.  The  department  may  cause to be vacated any dwelling or any part
  thereof which contains a nuisance as defined in  section  three  hundred
  nine,  or is occupied by more families or persons than permitted in this
  chapter, or is erected, altered or occupied contrary to  law.  Any  such
  dwelling  shall  not again be occupied until it or its occupancy, as the
  case may be, has been made to conform to law.