N.Y. CVP Law § 1001

§ 1001. Necessary joinder of parties. (a) Parties who should be\njoined. Persons who ought to be parties if complete relief is to be\naccorded between the persons who are parties to the action or who might\nbe inequitably affected by a judgment in the action shall be made\nplaintiffs or defendants. When a person who should join as a plaintiff\nrefuses to do so he may be made a defendant.\n (b) When joinder excused. When a person who should be joined under\nsubdivision (a) has not been made a party and is subject to the\njurisdiction of the court, the court shall order him summoned. If\njurisdiction over him can be obtained only by his consent or appearance,\nthe court, when justice requires, may allow the action to proceed\nwithout his being made a party. In determining whether to allow the\naction to proceed, the court shall consider:\n 1. whether the plaintiff has another effective remedy in case the\naction is dismissed on account of the nonjoinder;\n 2. the prejudice which may accrue from the nonjoinder to the defendant\nor to the person not joined;\n 3. whether and by whom prejudice might have been avoided or may in the\nfuture be avoided;\n 4. the feasibility of a protective provision by order of the court or\nin the judgment; and\n 5. whether an effective judgment may be rendered in the absence of the\nperson who is not joined.\n