The law forbids a landlord from unreasonably refusing permission to sublet, which is quite a bit different from not requiring permission in the first place.
2. (a) A tenant renting a residence pursuant to an existing lease in a dwelling having four or more residential units shall have the right to sublease his premises subject to the written consent of the landlord in advance of the subletting. Such consent shall not be unreasonably withheld.
(b) The tenant shall inform the landlord of his intent to sublease by mailing a notice of such intent by certified mail, return receipt requested. Such request shall be accompanied by the following information: (i) the term of the sublease, (ii) the name of the proposed sublessee, (iii) the business and permanent home address of the proposed sublessee, (iv) the tenant's reason for subletting, (v) the tenant's address for the term of the sublease, (vi) the written consent of any cotenant or guarantor of the lease, and (vii) a copy of the proposed sublease, to which a copy of the tenant's lease shall be attached if available, acknowledged by the tenant and proposed subtenant as being a true copy of such sublease. ...
(c) Within ten days after the mailing of such request, the landlord ...
...
5. Any sublet or assignment which does not comply with the provisions of this section shall constitute a substantial breach of lease or tenancy.
6. Any provision of a lease or rental agreement purporting to waive a provision of this section is null and void.
N.Y. RPP. LAW ยง 226-b : NY Code - Section 226-B: Right to sublease or assign - See more at: http://codes.lp.findlaw.com/nycode/RPP/7/226-b#sthash.y9ORKJ...
2. (a) A tenant renting a residence pursuant to an existing lease in a dwelling having four or more residential units shall have the right to sublease his premises subject to the written consent of the landlord in advance of the subletting. Such consent shall not be unreasonably withheld.
(b) The tenant shall inform the landlord of his intent to sublease by mailing a notice of such intent by certified mail, return receipt requested. Such request shall be accompanied by the following information: (i) the term of the sublease, (ii) the name of the proposed sublessee, (iii) the business and permanent home address of the proposed sublessee, (iv) the tenant's reason for subletting, (v) the tenant's address for the term of the sublease, (vi) the written consent of any cotenant or guarantor of the lease, and (vii) a copy of the proposed sublease, to which a copy of the tenant's lease shall be attached if available, acknowledged by the tenant and proposed subtenant as being a true copy of such sublease. ...
(c) Within ten days after the mailing of such request, the landlord ...
...
5. Any sublet or assignment which does not comply with the provisions of this section shall constitute a substantial breach of lease or tenancy.
6. Any provision of a lease or rental agreement purporting to waive a provision of this section is null and void.