N.Y. EPT Law § 13-2.1

§ 13-2.1 Agreements involving a contract to establish a trust, to make a\n testamentary provision of any kind, and by a personal\n representative to answer for the debt or default of a\n decedent, required to be in writing\n (a) Every agreement, promise or undertaking is unenforceable unless it\nor some note or memorandum thereof is in writing and subscribed by the\nparty to be charged therewith, or by his lawful agent, if such\nagreement, promise or undertaking:\n (1) Is a contract to establish a trust.\n (2) Is a contract to make a testamentary provision of any kind.\n (3) Is a promise by a personal representative to answer for the debt\nor default of his decedent.\n (b) A contract to make a joint will, or not to revoke a joint will, if\nexecuted after the effective date of this paragraph can be established\nonly by an express statement in the will that the instrument is a joint\nwill and that the provisions thereof are intended to constitute a\ncontract between the parties.\n