New York Codes, Rules and Regulations
Title 21 - Miscellaneous
Chapter XXIV - The Port Authority Of New York And New Jersey
Subchapter E - World Trade Center
Part 1290 - World Trade Center
Section 1290.2 - Entry restrictions

Persons shall use the common areas and facilities in the World Trade Center solely for purposes of ingress and egress, and no person shall cause any obstruction of or loiter in any such common area or facility. No person shall enter upon any court or roof area or parking area unless specifically so authorized by lease, permit, license or other agreement with the Port Authority. The Port Authority may exclude from buildings at the World Trade Center, between the hours of 6 p.m. and 8 a.m. and at all hours on Saturdays, Sundays and legal holidays, all persons who do not present a pass to the World Trade Center. All such passes shall be in such form as the manager of the World Trade Center may prescribe from time to time and no person shall issue passes unless authorized in writing by the manager to do so. Furthermore, if the Port Authority deems it advisable for security reasons, occupants of space at the World Trade Center and persons frequently doing business there shall provide and their employees shall wear or carry badges or other suitable means of identification which shall be subject to the prior approval of the Port Authority. Each person responsible for issuance of a pass or other means or identification to another person shall be liable to Port Authority for all acts or omissions of such other persons.