Section 28-503.5. Enforcement of order

On or after the tenth business day
  after the posting of such order and upon the written  directive  of  the
  commissioner,  police  officers  and  authorized  representatives of the
  department shall act upon and enforce such order by removing,  covering,
  painting over or otherwise rendering ineffective the illegal sign or its
  sign  structure  or both. Such work shall at all times be performed by a
  licensed sign hanger where required by  law.  Nothing  in  this  article
  shall  be  construed  to  prohibit  an  owner  or other person having an
  interest in the property from removing, or causing  the  removal  of  an
  illegal  sign  or  its  sign  structure  prior  to  the  arrival of such
  enforcement officers. On and after the posting of such removal order, no
  further permits for signs shall be issued for such building or  premises
  pursuant  to  this  code  and,  if the sign structure is not removed, no
  further display shall be exhibited on such  sign  structure  unless  and
  until the commissioner rescinds such order.