N.Y. Comp. Codes R. & Regs. Tit. 6 §§ 218-6.2
It is unlawful for any person to operate or leave standing upon any highway any motor vehicle that is required to be equipped with an air contaminant emission control system under this Part, or required to be equipped with an air contaminant emission control system pursuant to the Clean Air Act (42 U.S.C., section 7401 et seq.) (see Table 1, section 200.9 of this Title) and the standards and regulations promulgated thereunder, unless the motor vehicle is equipped with the required air contaminant emission control system which is correctly installed and in operating condition. Except when necessary to repair the vehicle air contaminant emissions control system or another part of the vehicle, it is unlawful for any person to disconnect, modify, or alter any such required device. Following such repair, the disconnected, modified or altered device must be correctly installed and in operating condition.
N.Y. Comp. Codes R. & Regs. Tit. 6 §§ 218-6.2