New York Codes, Rules and Regulations
Title 15 - Department of Motor Vehicles
Chapter I - REGULATIONS OF THE COMMISSIONER
Subchapter B - Registration, Certificate of Title, and Number Plates
Part 19 - New York City Auto Use Tax
Section 19.9 - Notification as to litigation

The Commissioner of Motor Vehicles shall promptly notify the corporation counsel of the city of New York, and the commissioner of finance shall promptly notify the deputy commissioner and counsel of the Department of Motor Vehicles, of any litigation instituted against either party which challenges the constitutionality or validity of the local law imposing the tax or of the enabling act pursuant to which it was adopted or which attempts to limit or question the applicability of either such law, and such notification shall include a copy of the papers served upon either party.