N.Y. C.P.L.R. 901

§ 901. Prerequisites to a class action. a. One or more members of a\nclass may sue or be sued as representative parties on behalf of all if:\n 1. the class is so numerous that joinder of all members, whether\notherwise required or permitted, is impracticable;\n 2. there are questions of law or fact common to the class which\npredominate over any questions affecting only individual members;\n 3. the claims or defenses of the representative parties are typical of\nthe claims or defenses of the class;\n 4. the representative parties will fairly and adequately protect the\ninterests of the class; and\n 5. a class action is superior to other available methods for the fair\nand efficient adjudication of the controversy.\n b. Unless a statute creating or imposing a penalty, or a minimum\nmeasure of recovery specifically authorizes the recovery thereof in a\nclass action, an action to recover a penalty, or minimum measure of\nrecovery created or imposed by statute may not be maintained as a class\naction.\n