2010 New York Code
MDW - Multiple Dwelling
Article 3 - (25) MULTIPLE DWELLINGS--GENERAL PROVISIONS
Title 2 - (50 - 68) FIRE PROTECTION AND SAFETY
51-C - Rights of tenants to install and maintain locks in certain entrance doors.

§  51-c.  Rights  of  tenants to install and maintain locks in certain
  entrance doors. Every tenant of a multiple dwelling, except a tenant  of
  a  multiple  dwelling  under  the supervision and control of a municipal
  housing authority, occupied by him, except  as  a  hotel  or  motel,  or
  college  or  school  dormitory,  shall  have  the  right  to install and
  maintain or cause to be installed and maintained in the entrance door of
  his particular housing unit in such multiple dwelling, a lock,  separate
  and  apart  from  any lock installed and maintained by the owner of such
  multiple dwelling, not more than three inches in  circumference,  as  an
  ordinary  incident to his tenancy, provided that a duplicate key to such
  lock shall be supplied to the landlord or his agent  upon  his  request;
  and  every  provision  of any lease hereafter made or entered into which
  reserves or provides for the payment by such tenant  of  any  additional
  rent,  bonus,  fee  or  other charge or any other thing of value for the
  right or privilege of installing and/or maintaining any such lock, shall
  be deemed to be void as against public policy and wholly unenforceable.