N.Y.C. Admin. Code § 28-503.5: § 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.